ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 40 Issue 5 > 2014,40(5):530-540. DOI:10.7519/j.issn.1000-0526.2014.05.002 Prev Next
Characteristics of Precipitation 30-60 d Oscillation over the Southeast of Tibetan Plateau in Summer 1998
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Abstract:
The characteristics of precipitation low frequency oscillation (LFO) over the southeast of Tibetan Plateau (TP) and especially the abnormal distribution and propagation of the 30-60 d filtered fields between positive and negative phases of precipitation LFO are investigated using daily NCEP/NCAR reanalysis and the observed daily rainfall data in 1998. The results are shown as follows: (1) There are several main periods of oscillation including the 10-20 d, 20-30 d and 30-60 d periods, and several significant rainfalls mainly occur in the positive phases of the 30-60 d oscillation, while significant negative rainfall anomaly in the negative phase. (2) During the positive (negative) phase, there is a low frequency cyclone (anticyclone) to the south side of the TP, and a low frequency anticyclone (cyclone) in the Sea of Japan. The southeast TP is influenced both by the southerly winds of the northeast side of the cyclone and the southerly winds of the southwest side of the anticyclone, and it is the low frequency moisture convergence (divergence) area. (3) During the positive phase, the southeast TP, Bay of Bengal (BOB) and South China Sea (SCS) are all low frequency heat source areas, but the 30-60 d filtered heat source/sink fields are opposite in the negative phase. (4) There exist westward propagating convergence (divergence) of moisture fluxes LFO and the 100 hPa divergence (convergence) LFO over the southeast TP which propagate from the West Pacific by the way of middle and lower reaches of Yangtze River, and they correspond well with the positive (negative) phase of precipitation LFO over the southeast TP when they propagate to the southeast TP.
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