The interannual variability of the temperature anomalies over the Tibetan Plateau (25-45°N, 75-105°E) is examined in relation to the Indian summer monsoon rainfall (ISMR: June to September total rainfall). For this purpose, the temperature anomaly data of the central-eastern Tibetan Plateau is divided into three regions using principal component analysis and the ISMR data for the period 1957-89 have been used. It is found that the January temperature anomaly of Region 2 has a significant negative relationship (r = −0.67) with the ISMR of the subsequent season. This region is located over the northeastern part of the Tibetan Plateau, mostly in Qinghai province, including the Bayan Harr Mountain range and the Qaidam Basin. This relationship is consistent and robust during the period of analysis and can be used to predict the strength of the Indian summer monsoon in the subsequent season. It was found that the January temperature anomaly in this region was associated with a persistent winter circulation pattern over the Eurasian continent during January through to March. Finally, the variation patterns of the temperature anomalies in all three regions over the central-eastern Tibetan Plateau during extreme years of the ISMR are examined. It is concluded that the January temperature anomaly over the northeastern Tibetan Plateau can be useful in forecasting the drought and flood conditions over India, especially in predicting the monsoon rainfall over the areas lying along the monsoon trough.
Utilizing 40 years of daily monsoon rainfall data averaged over 52, 2.5" x 2.5" latitude and longitude contiguous blocks covering the whole of India, we have investigated the relationship between monsoon onset at nine locations in India with the monsoon rainfall during the first 10,15,20, and 30 days of June and during the whole monsoon season. The onset is found to have a significant association only with rainfall observed during the subperiod of June, no significant correlations are found for the seasonal monsoon rainfall for any station. Interrelationships among onsets at these nine locations have also been studied. It is found that the arrival of the monsoon over the northern parts of the country has no relationship with the onset over Kerala. The relationship between the onset of the Baiu rains over 11 stations in Japan and the monsoon onset over India also has been studied by using 35 (1946-1980) years of data. Even though the onset of the Baiu over a few stations shows significant association with the monsoon onset over some stations of India, the relationship between the Baiu and monsoon onset is not very encouraging for linear prediction.KEY WORDS Monsoon onset monsoon advance relationships rainfall Baiu onset
In this paper, by using the Principal Component Analysis (PCA) technique monthly zonal wind indices over Tibetan Plateau (25°N–45°N, 75–105°E) (TP) at 200 hPa have been constructed for the period 1948–2006. These indices are referred as Tibetan Zonal Wind Index (TZWI). The relationship between the TZWI and Indian summer monsoon rainfall on monthly basis has been studied by the correlation analysis. From the analysis, it is observed that pre‐monsoon months (April and May) of TZWI show the significant inverse relationship with June and July rainfall over India respectively. The study may be useful for forecasting rainfall activity in June and July months, which are crucial months from the agricultural point of view.
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