ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 36,Issue 12,2010 Table of Contents
2010, 36(12):1-9.
DOI: 10.7519/j.issn.1000-0526.2010.12.001
Abstract:
The summer rainfall data in China represented by three reanalysis datasets (NCEP/DOE, ERA and JRA) are evaluated by comparing with the products of the station rainfall data in this study. Results show that the main characteritics of summer rainfall distribution in China are reasonably reproduced in three datasets, and most of the interannual and intraseasonal variations are captured. However, there are still some deficiencies in all of the three reanalysis rainfall products. In the NCEP product, an artificial rainfall center is located over the east periphery of the Tibetan Plateau, and the intraseasonal evolution of summer rainfall in midwestern and southwestern regions is poorly represented. In the ERA product, the rainfall amount is systematically underestimated and the interannual variation of rainfall over the midwestern regions is not well simulated. In the JRA product, the rainfall over coastal regions of South China is overestimated. The overestimation of weak rainfall and underestimation of heavy rainfall can be found in all of the three products. Concerning the TS and BS scores of the rainfall events with daily amount larger than 0.1 mm, the TS scrore is around 0.6 and the BS scrore is about 1.5 for all the reanalysis rainfall products. However, with the upgrade of rainfall rates, both of the scores decrease rapidly. The scores of torrential rain are very low for all reanalysis products. The analyses in this work not only indicate the capability of current advanced numerical models in simulating summer rainfall in China under the realistic circulation forcings, but also help to understand the simulation biases resulting from physical parameterization. Results would potentially contribute to the model development and evaluation in future.
The summer rainfall data in China represented by three reanalysis datasets (NCEP/DOE, ERA and JRA) are evaluated by comparing with the products of the station rainfall data in this study. Results show that the main characteritics of summer rainfall distribution in China are reasonably reproduced in three datasets, and most of the interannual and intraseasonal variations are captured. However, there are still some deficiencies in all of the three reanalysis rainfall products. In the NCEP product, an artificial rainfall center is located over the east periphery of the Tibetan Plateau, and the intraseasonal evolution of summer rainfall in midwestern and southwestern regions is poorly represented. In the ERA product, the rainfall amount is systematically underestimated and the interannual variation of rainfall over the midwestern regions is not well simulated. In the JRA product, the rainfall over coastal regions of South China is overestimated. The overestimation of weak rainfall and underestimation of heavy rainfall can be found in all of the three products. Concerning the TS and BS scores of the rainfall events with daily amount larger than 0.1 mm, the TS scrore is around 0.6 and the BS scrore is about 1.5 for all the reanalysis rainfall products. However, with the upgrade of rainfall rates, both of the scores decrease rapidly. The scores of torrential rain are very low for all reanalysis products. The analyses in this work not only indicate the capability of current advanced numerical models in simulating summer rainfall in China under the realistic circulation forcings, but also help to understand the simulation biases resulting from physical parameterization. Results would potentially contribute to the model development and evaluation in future.
2010, 36(12):10-18.
DOI: 10.7519/j.issn.1000-0526.2010.12.002
Abstract:
Given the nonlinear and complex nature of atmospheric system combined with the uncertainties associated with initial conditions and models, it is not only a requirement from science but also a necessity to better serve user community to transit weather prediction from deterministic to probabilistic format. However, the reason behind the transition is not clear but full of debate and confusion to many including public, endusers and even meteorologists themselves. To clarify some of these and to expedite the transition, a few issues were discussed. The ensemble forecasting which is a central technique to facilitate such a transition has been discussed in the companion paper of this article. In this paper, a few other issues related to ensemblebased probabilistic forecasts were discussed, which include (1) how to measure the merits of a probabilistic forecast? (2) how to use probabilistic information in decisionmaking process? and (3) why an ensemblebased probabilistic forecast has, in general, more utility or economical value than a singlevalue deterministic forecast does? To be easily understood and applicable to real world situations by readers especially forecasters and endusers, plain language illustrated with examples was used to explain the related concepts.
Given the nonlinear and complex nature of atmospheric system combined with the uncertainties associated with initial conditions and models, it is not only a requirement from science but also a necessity to better serve user community to transit weather prediction from deterministic to probabilistic format. However, the reason behind the transition is not clear but full of debate and confusion to many including public, endusers and even meteorologists themselves. To clarify some of these and to expedite the transition, a few issues were discussed. The ensemble forecasting which is a central technique to facilitate such a transition has been discussed in the companion paper of this article. In this paper, a few other issues related to ensemblebased probabilistic forecasts were discussed, which include (1) how to measure the merits of a probabilistic forecast? (2) how to use probabilistic information in decisionmaking process? and (3) why an ensemblebased probabilistic forecast has, in general, more utility or economical value than a singlevalue deterministic forecast does? To be easily understood and applicable to real world situations by readers especially forecasters and endusers, plain language illustrated with examples was used to explain the related concepts.
2010, 36(12):19-27.
DOI: 10.7519/j.issn.1000-0526.2010.12.003
Abstract:
There was a torrential rain occurring in Beijing during 15:00—18：00 BT 10 August 2008, and it was the afternoon of that day there were three mesoβ convective cells that moved to city of Beijing, generated heavy rainfall (can be 45 mm/h and 12 mm/5 min) and had an obvious organizational development. Many high spatialtemporal resolution data, such as autoweather station (AWS) network data, Doppler radar data, wind profile data and variational Doppler radar analysis system (VDRAS), are used to analyze the organizational development of the mesoscale convective system in this case. It is revealed that: (1) the cause for the organizational development of three convective cells in the afternoon is about the appearance of mesoβ shear which was in the front of stratified precipitation system; (2) there are obvious changes before starting to rain in main urban areas of Beijing, such as accumulation of CAPE, and environmental wind whose direction changed from south to east; (3) the casue for the origanizational development of the three convective cells is due to the shear generated by the confliction between the northwest cold horizontal flow from stratified rain system and the southeast warm horizontal flow beneath 500 m. Therefore, at the advantaged largescale background, with regard to the weather forecast of largescale rain event, one of the key places is in the front of stratified precipitation system, where conflict between the cold horizontal flow and the environmental wind before the system maybe triggers the organizational development of convective system.
There was a torrential rain occurring in Beijing during 15:00—18：00 BT 10 August 2008, and it was the afternoon of that day there were three mesoβ convective cells that moved to city of Beijing, generated heavy rainfall (can be 45 mm/h and 12 mm/5 min) and had an obvious organizational development. Many high spatialtemporal resolution data, such as autoweather station (AWS) network data, Doppler radar data, wind profile data and variational Doppler radar analysis system (VDRAS), are used to analyze the organizational development of the mesoscale convective system in this case. It is revealed that: (1) the cause for the organizational development of three convective cells in the afternoon is about the appearance of mesoβ shear which was in the front of stratified precipitation system; (2) there are obvious changes before starting to rain in main urban areas of Beijing, such as accumulation of CAPE, and environmental wind whose direction changed from south to east; (3) the casue for the origanizational development of the three convective cells is due to the shear generated by the confliction between the northwest cold horizontal flow from stratified rain system and the southeast warm horizontal flow beneath 500 m. Therefore, at the advantaged largescale background, with regard to the weather forecast of largescale rain event, one of the key places is in the front of stratified precipitation system, where conflict between the cold horizontal flow and the environmental wind before the system maybe triggers the organizational development of convective system.
2010, 36(12):28-34.
DOI: 10.7519/j.issn.1000-0526.2010.12.004
Abstract:
Based on the observational data obtained from the 50mtower on the south bank of the Yangtze River in Huangshi, the paper has made detailed studies on two rainstorms occurring in 31 May and 1-2 July, 2007 respectively. The unusual characteristics can provide the basis to further know rainstorm’s surface layer physical process in Huangshi area. The results show that: (1) Before the rainstorm, the temperature drops together with the humidity rise, the direction of wind changes, and the horizontal wind speed and vertical airflow speed increase obviously. After the rainstorm, the wind direction changes gently and the wind speed increases once more; (2) The vertical airflow speed oscillates rapidly before the rainstorm, stimulating the turbulence; (3) The turbulent kinetic energy reaches the obvious peak and the flux transports the momentum and heat to the higher level, the turbulent intensity increases gradually. The maximal value of the turbulent kinetic energy appears ahead of the flux. The turbulence enhances when approaching rainfall. That is, obvious changes of the physical quantity field occur before and after rainstorm，the turbulence heightens ahead of the rainstorm.
Based on the observational data obtained from the 50mtower on the south bank of the Yangtze River in Huangshi, the paper has made detailed studies on two rainstorms occurring in 31 May and 1-2 July, 2007 respectively. The unusual characteristics can provide the basis to further know rainstorm’s surface layer physical process in Huangshi area. The results show that: (1) Before the rainstorm, the temperature drops together with the humidity rise, the direction of wind changes, and the horizontal wind speed and vertical airflow speed increase obviously. After the rainstorm, the wind direction changes gently and the wind speed increases once more; (2) The vertical airflow speed oscillates rapidly before the rainstorm, stimulating the turbulence; (3) The turbulent kinetic energy reaches the obvious peak and the flux transports the momentum and heat to the higher level, the turbulent intensity increases gradually. The maximal value of the turbulent kinetic energy appears ahead of the flux. The turbulence enhances when approaching rainfall. That is, obvious changes of the physical quantity field occur before and after rainstorm，the turbulence heightens ahead of the rainstorm.
2010, 36(12):35-40.
DOI: 10.7519/j.issn.1000-0526.2010.12.005
Abstract:
With the developing of China aerospace tracking & control, the application of meteorological support to ocean ship, becomes more and more important, especially in the India Ocean and the South Pacific Ocean. On the contrary, we knew little about the weathers there which could bring strong winds and big waves over those areas. In the study, by using related climate data, some analyses are conducted on active behaviors of several weather systems and weather cases, which were different from ones in the Northern Hemisphere. Also in this paper, some advices are proposed to weather man in order to help them providing more accurate weather prediction to the navigating ship.
With the developing of China aerospace tracking & control, the application of meteorological support to ocean ship, becomes more and more important, especially in the India Ocean and the South Pacific Ocean. On the contrary, we knew little about the weathers there which could bring strong winds and big waves over those areas. In the study, by using related climate data, some analyses are conducted on active behaviors of several weather systems and weather cases, which were different from ones in the Northern Hemisphere. Also in this paper, some advices are proposed to weather man in order to help them providing more accurate weather prediction to the navigating ship.
CHEN Jing
,
TONG Hua
,
XU Zhifang
,
DENG Guo
,
DENG Liantang
,
CHEN Yun
,
XIAO Dan
,
CUI Yingjie
,
WANG Xiaocong
,
ZHU Guofu
,
HU Jiangkai
,
GONG Jiandong
2010, 36(12):41-49.
DOI: 10.7519/j.issn.1000-0526.2010.12.006
Abstract:
The numerical weather prediction (NWP) products aiming to severe weather prediction, including T639, GRAPES_RUC,WRFEPS, were developed by Numerical Weather Prediction Division, NMC. Through the analysis of the squall line weather occurring in Henan Province on 3 June, 2009, it is showed that the high resolution models have improved to some extent forecasting severe weather. But the 15 km resolution is not so good enough to forecast severe weather. Higher temporal and spatial resolution is needed to better reveal the evolation of severe convection weather in the application of the NWP products.
The numerical weather prediction (NWP) products aiming to severe weather prediction, including T639, GRAPES_RUC,WRFEPS, were developed by Numerical Weather Prediction Division, NMC. Through the analysis of the squall line weather occurring in Henan Province on 3 June, 2009, it is showed that the high resolution models have improved to some extent forecasting severe weather. But the 15 km resolution is not so good enough to forecast severe weather. Higher temporal and spatial resolution is needed to better reveal the evolation of severe convection weather in the application of the NWP products.
2010, 36(12):50-55.
DOI: 10.7519/j.issn.1000-0526.2010.12.007
Abstract:
The radar quantitative precipitation estimation (QPE) technology is applied to gain the high resolution rainfall information at time and space scales, and the latter is taken as the input of hydrological model to improve the precision of flood forecast. The paper takes the Bailianhe Basin as research area, and applies the grouping relationship of Z and I to transform the radar reflectivity into the precipitation, and then uses the Kalman filtering method to adjust the precipitation transformed from radar data using the precipitation detected by rain gauge as the criterion. And then, we input different precipitation data into the Xinanjiang model to make the flood forecast test. The results show that if the radar QPE without revision is taken as the input of hydrological model, the forecast precision is not ideal, but when the radar QPE is revised, the forecast precision gets improvement.
The radar quantitative precipitation estimation (QPE) technology is applied to gain the high resolution rainfall information at time and space scales, and the latter is taken as the input of hydrological model to improve the precision of flood forecast. The paper takes the Bailianhe Basin as research area, and applies the grouping relationship of Z and I to transform the radar reflectivity into the precipitation, and then uses the Kalman filtering method to adjust the precipitation transformed from radar data using the precipitation detected by rain gauge as the criterion. And then, we input different precipitation data into the Xinanjiang model to make the flood forecast test. The results show that if the radar QPE without revision is taken as the input of hydrological model, the forecast precision is not ideal, but when the radar QPE is revised, the forecast precision gets improvement.
2010, 36(12):56-61.
DOI: 10.7519/j.issn.1000-0526.2010.12.008
Abstract:
The precipitation in forecast period greatly influences flood forecasting precision. The longer the forecast period is, the bigger the influence of the precipitation in forecast period on flood forecast will be, therefore the people more and more pay attention to the precipitation in forecast period. The paper uses the rainfall information that the mesoscale numer〖HJ〗ical model (AREM Model) forecast takes as the precipitation in forecast period, and inputs into the Xinanjiang hydrological model, to make the forecast experiments on flood process in flood season in 2008 in research area. The results show that the flood forecasts can be improved obviously when considering the precipitation in forecast period, and the numerical model forecast will have an expansive application prospect in the hydrology forecast.
The precipitation in forecast period greatly influences flood forecasting precision. The longer the forecast period is, the bigger the influence of the precipitation in forecast period on flood forecast will be, therefore the people more and more pay attention to the precipitation in forecast period. The paper uses the rainfall information that the mesoscale numer〖HJ〗ical model (AREM Model) forecast takes as the precipitation in forecast period, and inputs into the Xinanjiang hydrological model, to make the forecast experiments on flood process in flood season in 2008 in research area. The results show that the flood forecasts can be improved obviously when considering the precipitation in forecast period, and the numerical model forecast will have an expansive application prospect in the hydrology forecast.
2010, 36(12):62-67.
DOI: 10.7519/j.issn.1000-0526.2010.12.009
Abstract:
Based on the observation data and records at 85 observation stations in Jiangxi Province during 1959-2004, spatialtemporal characteristics of hailstorm and intense gust in Jiangxi are investigated by using multiple statistics. Major results are as follows: Hail often occurs in the central and west parts of the province with four extreme centers, while intense gust occurs in the central and north plains with two centers. In terms of seasonal variations, the temporal distributions of hail is categorized as onepeak type, and is more likely to occur from March to May and most frequent in April. While gust shows a doublepeak distribution, indicating the concentration of gust between March and August, with one peak during the period of March to May and the other peak from June to August. From spring to summer in the past 46 years, the abrupt climate change of gust shows that its frequency has decreased in Jiangxi since 1992, while the interdecadal variation of hail has not demonstrated obvious climate abruption. Hail varies by a 12a scale before 1981 with three periods, while after 1981 it becomes an 18a cycle and at the same time with 4 periods on a 9a scale. The middle to highfrequency variations are dominated for the gust, showing a 12a scale before 1973 and a 6a cycle after 1974. The first mode of EOF indicates that the variation trend is consistent for hail and intense gust. According to the second mode of EOF, the spatial variation of hail and gust in the plain shows a reverse trend in relation to mountainous areas, especially gust in the south Jiangxi.
Based on the observation data and records at 85 observation stations in Jiangxi Province during 1959-2004, spatialtemporal characteristics of hailstorm and intense gust in Jiangxi are investigated by using multiple statistics. Major results are as follows: Hail often occurs in the central and west parts of the province with four extreme centers, while intense gust occurs in the central and north plains with two centers. In terms of seasonal variations, the temporal distributions of hail is categorized as onepeak type, and is more likely to occur from March to May and most frequent in April. While gust shows a doublepeak distribution, indicating the concentration of gust between March and August, with one peak during the period of March to May and the other peak from June to August. From spring to summer in the past 46 years, the abrupt climate change of gust shows that its frequency has decreased in Jiangxi since 1992, while the interdecadal variation of hail has not demonstrated obvious climate abruption. Hail varies by a 12a scale before 1981 with three periods, while after 1981 it becomes an 18a cycle and at the same time with 4 periods on a 9a scale. The middle to highfrequency variations are dominated for the gust, showing a 12a scale before 1973 and a 6a cycle after 1974. The first mode of EOF indicates that the variation trend is consistent for hail and intense gust. According to the second mode of EOF, the spatial variation of hail and gust in the plain shows a reverse trend in relation to mountainous areas, especially gust in the south Jiangxi.
2010, 36(12):68-73.
DOI: 10.7519/j.issn.1000-0526.2010.12.010
Abstract:
Based on the monthly precipitation data of four typical stations (Lhasa, Zetang, Xigaze and Gyangze) from 1960 to 2006 in the flood season, the periodic variation of precipitation over 47 years has been analyzed by Mexican hat wavelet analysis. It shows that there are remarkable periodic oscillations of 14-16 a and 2-4 a in the middle reaches of the Yarlung Zangbo River, and stations Xigaze and Gyangze have mainly periodic oscillations of 14-16 a, and stations Lhasa and Zetang with periodic oscillations of 2-4 a. There are eight cycles of droughts and floods in the periodic oscillation of 14-16 a and it shows notable periodic oscillations of 2-4 a in 1964-1976 and 1984-1997. The periodic oscillation of 8 a becomes remarkable after the middle of 1970s. During the past 47 years, the phases of oscillation at different time scales are superimposed in five time periods, leading to extraordinarily heavy precipitation over these periods.
Based on the monthly precipitation data of four typical stations (Lhasa, Zetang, Xigaze and Gyangze) from 1960 to 2006 in the flood season, the periodic variation of precipitation over 47 years has been analyzed by Mexican hat wavelet analysis. It shows that there are remarkable periodic oscillations of 14-16 a and 2-4 a in the middle reaches of the Yarlung Zangbo River, and stations Xigaze and Gyangze have mainly periodic oscillations of 14-16 a, and stations Lhasa and Zetang with periodic oscillations of 2-4 a. There are eight cycles of droughts and floods in the periodic oscillation of 14-16 a and it shows notable periodic oscillations of 2-4 a in 1964-1976 and 1984-1997. The periodic oscillation of 8 a becomes remarkable after the middle of 1970s. During the past 47 years, the phases of oscillation at different time scales are superimposed in five time periods, leading to extraordinarily heavy precipitation over these periods.
2010, 36(12):74-79.
DOI: 10.7519/j.issn.1000-0526.2010.12.011
Abstract:
With the daily observational data at 93 meteorological stations in Heilongjiang, Jilin, Liaoning and eastern Inner Mongolia in the past 50 years (1958-2007), the spatial and temporal distribution characteristics of heavy snowfall in Northeast China are analyzed. The results show as follows: First, heavy snowfall in this area is obviously distributed by seasons, and most of the heavy snowfall are in spring (March-April) and fall (October-November). Second, heavy snowfall in this area is also obviously distributed by regions, and most of the heavy snowfall are in southeastern Changbai Mountains, southern Liaodong Peninsula and northwestern Da Hinggan Mountains. Third, the yearly total precipitation of heavy snowfall in the past nearly 50 years almost didn’t change, but the heavy snowfall precipitation of spring (fall) in Northeast China tends to be more (less).
With the daily observational data at 93 meteorological stations in Heilongjiang, Jilin, Liaoning and eastern Inner Mongolia in the past 50 years (1958-2007), the spatial and temporal distribution characteristics of heavy snowfall in Northeast China are analyzed. The results show as follows: First, heavy snowfall in this area is obviously distributed by seasons, and most of the heavy snowfall are in spring (March-April) and fall (October-November). Second, heavy snowfall in this area is also obviously distributed by regions, and most of the heavy snowfall are in southeastern Changbai Mountains, southern Liaodong Peninsula and northwestern Da Hinggan Mountains. Third, the yearly total precipitation of heavy snowfall in the past nearly 50 years almost didn’t change, but the heavy snowfall precipitation of spring (fall) in Northeast China tends to be more (less).
2010, 36(12):80-85.
DOI: 10.7519/j.issn.1000-0526.2010.12.012
Abstract:
Using 40year meteorological data at 660 conventional stations in China, the influence of direct interpolation （DI） and integrated remainder method （IRM） on temperature was analyzed by 3 intepolation methods of IDW, Kriging and Spline. A method of removing deterministic part in temperature was put forward which can improve temperature calculation precision. The error was contrasted from time to space and the interpolation sensitivity to station density was investigated finally. The result shows that: excluding some months， mean absolute error （MAE） of IRM was in 1 ℃ which was 0.6-1.6 ℃ lower than DI, the precision was improved by 38％-85％. The precision of IRM did not rely on station density and interpolation method which has a high accuracy and stability. That means it is not the main accesses of increasing observation stations and modifying interpolation methods on improving precision of temperature calculation.
Using 40year meteorological data at 660 conventional stations in China, the influence of direct interpolation （DI） and integrated remainder method （IRM） on temperature was analyzed by 3 intepolation methods of IDW, Kriging and Spline. A method of removing deterministic part in temperature was put forward which can improve temperature calculation precision. The error was contrasted from time to space and the interpolation sensitivity to station density was investigated finally. The result shows that: excluding some months， mean absolute error （MAE） of IRM was in 1 ℃ which was 0.6-1.6 ℃ lower than DI, the precision was improved by 38％-85％. The precision of IRM did not rely on station density and interpolation method which has a high accuracy and stability. That means it is not the main accesses of increasing observation stations and modifying interpolation methods on improving precision of temperature calculation.
2010, 36(12):86-93.
DOI: 10.7519/j.issn.1000-0526.2010.12.013
Abstract:
Based on the daily temperature data during years 1961—2008, the variation regularity and relationship of the extreme high temperature indices (extreme, absolute and relative threshold indices) and its response to regional warming in the Three Gorges reservoir area were analyzed, and the changing characteristics of the high temperature days of the Three Gorges reservoir area in summer and its circulation patterns in anomalous years were studied. The results showed that the interdecadal variation of the extreme high temperature indices was the same as the average annual temperature in the recent 48 years. The variation performed a downward trend before the early 1980s, and then converted to an upward trend. The yearly change shows that in the 1980s both are low and high in other years. The relative threshold indices (HWDI,WSDI and TX90p) in the low/high years all have better consistency than the annual average temperature in the linear tendency and the correlation coefficient. The correlation analysis gave great idea on the relationship of both the extreme indices and the absolute threshold indices and the extreme indices together with the relative threshold indices. However, the relationship of the extreme indices/the absolute threshold indices and the relative threshold indices is not so optimistic. The circulation patterns have the obvious difference between in hot summer years and in cool summer years．There are not continuing block highs in Okhotsk Sea and Ural Mountains, the East Asian trough become weak, the West Pacific subtropical high retreated eastward and shifted northward， and the updraft over the Tibetan Plateau is weak． These circulation patterns are advantageous to the genesis and development of the high temperature and drought in the Three Gorges reservoir area．
Based on the daily temperature data during years 1961—2008, the variation regularity and relationship of the extreme high temperature indices (extreme, absolute and relative threshold indices) and its response to regional warming in the Three Gorges reservoir area were analyzed, and the changing characteristics of the high temperature days of the Three Gorges reservoir area in summer and its circulation patterns in anomalous years were studied. The results showed that the interdecadal variation of the extreme high temperature indices was the same as the average annual temperature in the recent 48 years. The variation performed a downward trend before the early 1980s, and then converted to an upward trend. The yearly change shows that in the 1980s both are low and high in other years. The relative threshold indices (HWDI,WSDI and TX90p) in the low/high years all have better consistency than the annual average temperature in the linear tendency and the correlation coefficient. The correlation analysis gave great idea on the relationship of both the extreme indices and the absolute threshold indices and the extreme indices together with the relative threshold indices. However, the relationship of the extreme indices/the absolute threshold indices and the relative threshold indices is not so optimistic. The circulation patterns have the obvious difference between in hot summer years and in cool summer years．There are not continuing block highs in Okhotsk Sea and Ural Mountains, the East Asian trough become weak, the West Pacific subtropical high retreated eastward and shifted northward， and the updraft over the Tibetan Plateau is weak． These circulation patterns are advantageous to the genesis and development of the high temperature and drought in the Three Gorges reservoir area．
2010, 36(12):94-101.
DOI: 10.7519/j.issn.1000-0526.2010.12.014
Abstract:
The characteristics of atmospheric physical environment in urban areas are to a large extent determined by the status of underlying surface. An increase in the urban natural surface such as wetlands may help decrease surface temperature, increase humidity, change local flow field, and improve local micrometeorological conditions and atmosphere physical environment. The multiscale numerical modeling system provides an effective method for assessing quantitatively the atmospheric physical environment in urban planning. In this paper an Urban Scale Model in the system is used to simulate the variability of surface air temperature, humidity, wind velocity, atmospheric diffusion conditions and their effect on urban atmospheric environment on condition of the dispersed or converged water layout with the proportion of urban water area in urban area being 4%, 8%, 12% and 16%, respectively. Based on meteorological observation data at urban water body sites in Beijing, the differences of air temperature and humidity among the area surrounding water body, commercial areas and traffic zones are analyzed and the simulated results are compared. The results reveal that the layout of urban water body has an obvious effect on urban micrometeorological environment. No matter whether the layout is dispersed or converged, the increase of urban water body area to a certain extent leads to the decrease of surface air temperature, increase of humidity, and enlargement of wind velocity. But water body in the dispersed distribution has a more significant effect on the urban micrometeorological environment than that in the converged distribution.
The characteristics of atmospheric physical environment in urban areas are to a large extent determined by the status of underlying surface. An increase in the urban natural surface such as wetlands may help decrease surface temperature, increase humidity, change local flow field, and improve local micrometeorological conditions and atmosphere physical environment. The multiscale numerical modeling system provides an effective method for assessing quantitatively the atmospheric physical environment in urban planning. In this paper an Urban Scale Model in the system is used to simulate the variability of surface air temperature, humidity, wind velocity, atmospheric diffusion conditions and their effect on urban atmospheric environment on condition of the dispersed or converged water layout with the proportion of urban water area in urban area being 4%, 8%, 12% and 16%, respectively. Based on meteorological observation data at urban water body sites in Beijing, the differences of air temperature and humidity among the area surrounding water body, commercial areas and traffic zones are analyzed and the simulated results are compared. The results reveal that the layout of urban water body has an obvious effect on urban micrometeorological environment. No matter whether the layout is dispersed or converged, the increase of urban water body area to a certain extent leads to the decrease of surface air temperature, increase of humidity, and enlargement of wind velocity. But water body in the dispersed distribution has a more significant effect on the urban micrometeorological environment than that in the converged distribution.
2010, 36(12):102-108.
DOI: 10.7519/j.issn.1000-0526.2010.12.015
Abstract:
Simulation of dynamic soil moisture in farmland is the important basis of agricultural water management. Based on the water balance equation of root zone, and taking the lower boundary water flux of root zone into account, a farmland soil moisture simulation model was set up, in cluding crop evapotranspiration model, lower boundary water flux model and water balance equation. The parameters of the model were fixed by the observation data of soil moisture through the winter wheat growing season in the irrigation experimental base of Shanxi Technical College of Water Conservancy in 2007 and 2008. The soil moisture simulated by the model agreed well with the measured ones, the multiple correlation coefficient reached 0.9555; and the F test reached extremely significance level. The established farmland soil moisture simulation model can be used to calculate crop evapotranspiration, lower boundary water flux in root zone and field soil moisture; and the mean calculation precision can reach 3%-11%.The result shows that the model deals well with the field soil water transform process.
Simulation of dynamic soil moisture in farmland is the important basis of agricultural water management. Based on the water balance equation of root zone, and taking the lower boundary water flux of root zone into account, a farmland soil moisture simulation model was set up, in cluding crop evapotranspiration model, lower boundary water flux model and water balance equation. The parameters of the model were fixed by the observation data of soil moisture through the winter wheat growing season in the irrigation experimental base of Shanxi Technical College of Water Conservancy in 2007 and 2008. The soil moisture simulated by the model agreed well with the measured ones, the multiple correlation coefficient reached 0.9555; and the F test reached extremely significance level. The established farmland soil moisture simulation model can be used to calculate crop evapotranspiration, lower boundary water flux in root zone and field soil moisture; and the mean calculation precision can reach 3%-11%.The result shows that the model deals well with the field soil water transform process.
2010, 36(12):109-115.
DOI: 10.7519/j.issn.1000-0526.2010.12.016
Abstract:
To study changes of land use status and vegetation coverage pre and post returning farmland to forest, the TM remote sensing images were interpreted, revealing the practical effectiveness for ecological construction project of Wuqi County, Shaanxi Province by returning farmland to forestry. Based on the air temperature and soil temperature 37year data at 6 meteorological stations surrounding Wuqi County, the effects of the land cover change on temperature in this area have been analyzed. The results showed that Wuqi County layout appears gradually, and has become increasingly clear with the implementation of the project of returning farmland to forest. Meanwhile, the vegetation coverage increases significantly, the high vegetation coverage area is increasing year by year, the low vegetation coverage area is just decreasing, and the vegetation restoration is significantly better than the surrounding area. Compared with 1997, the 75.15% of arable land is no longer farmed by 2007, the withdrawal of the main arable land turns into grassland, woodland and orchards; and the vegetation coverage has increased significantly, from 37.06% in 1997 to 80.60% in 2007. There has an impact on the air temperature and soil temperature after vegetation cover changes, warming trend is declining, the impact of the summer is greater than in winter, and the night time than during the day.
To study changes of land use status and vegetation coverage pre and post returning farmland to forest, the TM remote sensing images were interpreted, revealing the practical effectiveness for ecological construction project of Wuqi County, Shaanxi Province by returning farmland to forestry. Based on the air temperature and soil temperature 37year data at 6 meteorological stations surrounding Wuqi County, the effects of the land cover change on temperature in this area have been analyzed. The results showed that Wuqi County layout appears gradually, and has become increasingly clear with the implementation of the project of returning farmland to forest. Meanwhile, the vegetation coverage increases significantly, the high vegetation coverage area is increasing year by year, the low vegetation coverage area is just decreasing, and the vegetation restoration is significantly better than the surrounding area. Compared with 1997, the 75.15% of arable land is no longer farmed by 2007, the withdrawal of the main arable land turns into grassland, woodland and orchards; and the vegetation coverage has increased significantly, from 37.06% in 1997 to 80.60% in 2007. There has an impact on the air temperature and soil temperature after vegetation cover changes, warming trend is declining, the impact of the summer is greater than in winter, and the night time than during the day.
2010, 36(12):116-121.
DOI: 10.7519/j.issn.1000-0526.2010.12.017
Abstract:
The following are the main characteristics of the general circulation of atmosphere in September 2010. The polar vortex center over the Northern Hemisphere is single. The circulation presents a fourwave pattern in middlehigh latitudes. A negative anomaly with more than 120 gpm difference is found over the sea east of Iceland on 500 hPa geopotential height field. The intensity of the subtropical high over the Northwest Pacific is stronger than the corresponding period of normal years. The location for the west ridge spot is near 24°N, 100°E, which is more northerly and more west than normal years. The monthly mean temperature (17.1 ℃) is 1.1 ℃ higher than the same period of normal years and the national mean precipitation (85.1 mm) is 19.7 mm more than the same period of normal years. In this month, there were 3 obvious cold air processes and 7 precipitation processes, 4 tropical cyclones generated, which were named Malou, Meranti, Fanapi, and Malakas respectively, in which Meranti and Fanapi landed in China and resulted in heavy damages.
The following are the main characteristics of the general circulation of atmosphere in September 2010. The polar vortex center over the Northern Hemisphere is single. The circulation presents a fourwave pattern in middlehigh latitudes. A negative anomaly with more than 120 gpm difference is found over the sea east of Iceland on 500 hPa geopotential height field. The intensity of the subtropical high over the Northwest Pacific is stronger than the corresponding period of normal years. The location for the west ridge spot is near 24°N, 100°E, which is more northerly and more west than normal years. The monthly mean temperature (17.1 ℃) is 1.1 ℃ higher than the same period of normal years and the national mean precipitation (85.1 mm) is 19.7 mm more than the same period of normal years. In this month, there were 3 obvious cold air processes and 7 precipitation processes, 4 tropical cyclones generated, which were named Malou, Meranti, Fanapi, and Malakas respectively, in which Meranti and Fanapi landed in China and resulted in heavy damages.
2010, 36(12):122-127.
DOI: 10.7519/j.issn.1000-0526.2010.12.018
Abstract:
According to the characteristics of CINRAD / SA, SB radar receiver, this article discusses the process of the receiver test channel, the signal main channel and transmitter test signal, which is related to the echo intensity calibration. Based on years of experience in weather radar technology security, this artilce discusses in detail the fault diagnosis method of echo intensity calibration, summarizes the fault diagnosis process of echo intensity calibration, and lists three examples in which the above falut diagnosis and solution are used to exclude the fault resulting from the receiver test channel, the signal main channel and the RF leakage signal of transmitter.This articles explains the importance of the fault diagnosis in CINRAD technology support and guarantee and makes some advices about it.
According to the characteristics of CINRAD / SA, SB radar receiver, this article discusses the process of the receiver test channel, the signal main channel and transmitter test signal, which is related to the echo intensity calibration. Based on years of experience in weather radar technology security, this artilce discusses in detail the fault diagnosis method of echo intensity calibration, summarizes the fault diagnosis process of echo intensity calibration, and lists three examples in which the above falut diagnosis and solution are used to exclude the fault resulting from the receiver test channel, the signal main channel and the RF leakage signal of transmitter.This articles explains the importance of the fault diagnosis in CINRAD technology support and guarantee and makes some advices about it.
2010, 36(12):128-133.
DOI: 10.7519/j.issn.1000-0526.2010.12.019
Abstract:
Using the Xingyi new generation of Doppler weather radar complex scan data and WSR88D storm cell identification and tracking (SCIT) algorithm, the 40 weather courses occurring in Southwest Guizhou Province in 2007 to 2008 were assessed and analyzed from the six aspects: cell identification, assessment of cell track, cell location prediction, the relationship with the assessing effect， the relation with the assessing effect and the distance， and the comparative analysis between the hail weather and the heavy rainfall. Under the background of taking full account of local geography and climate, the unfavorable situation for algorithm assessment is made analysis and compensation and proposed solutions. First, to lower identification threshold, so that the 7 SCIT reflectivity thresholds are degraded by one level; Second, the vertical reflectivity gradient method is used. With the improved algorithm the weather cases occurring in 2007 and 2008 were reassessed and reanalyzed, and the comparative results show that the improved algorithm enhances the effect to some extent.
Using the Xingyi new generation of Doppler weather radar complex scan data and WSR88D storm cell identification and tracking (SCIT) algorithm, the 40 weather courses occurring in Southwest Guizhou Province in 2007 to 2008 were assessed and analyzed from the six aspects: cell identification, assessment of cell track, cell location prediction, the relationship with the assessing effect， the relation with the assessing effect and the distance， and the comparative analysis between the hail weather and the heavy rainfall. Under the background of taking full account of local geography and climate, the unfavorable situation for algorithm assessment is made analysis and compensation and proposed solutions. First, to lower identification threshold, so that the 7 SCIT reflectivity thresholds are degraded by one level; Second, the vertical reflectivity gradient method is used. With the improved algorithm the weather cases occurring in 2007 and 2008 were reassessed and reanalyzed, and the comparative results show that the improved algorithm enhances the effect to some extent.
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