The Relationship between Sea Surface Temperature in the Bay of Bengal and Monsoon Rainfall in Bangladesh, 1912-2001
To explore the signature pattern between sea surface temperature (SST) and summer monsoon rainfall in Bangladesh, the study examined 90 years (1912-2001) of monthly rainfall data for twelve stations for the months of May (pre-monsoon month), and June through September (monsoon months) and SST of the Bay of Bengal for the period of 1912 through 2001 at 2° by 2° grid cells. The total number of observation for each station was 450. In order to understand and explore the notion of the signature, two classical statistical methods, Principal Component Analysis and Canonical Correlation Analysis, were used to analyze the data. For data analysis and graphics, statistical software package SPSS and S-Plus programming environment were used. Also, mapping softwares ArcView, ArcGIS and ArcCatalog were used for making maps in order to show the results of each criteria variable. There is a significant positive (0.64) relationship between the All-Bangladesh Monsoon Rainfall (ABMR) and SST over the Bay of Bengal in the month of June. Any other monthly correlation was not found to be significant, although the overall correlation (i.e., May through September) existed between the SST and ABMR. They were poorly correlated. The SST over the Bay of Bengal was positively correlated with the June rainfall in Bangladesh, especially highly correlated with the Comilla station. The SST over the Bay of Bengal was important at 89°, 93°, and 95° longitudes for predicting the June rainfall in Bangladesh. The prevailing wind had a south-easterly component at this station. This is due to the deflection of the wind caused by the coastal hills. The orographic effect in the east and north-eastern part of the country enhanced the rainfall amount in that area. The correlations between the SST and monsoon rainfall in Bangladesh for the months of May, July, August, and September were found to be zero. Neither of the canonical correlations was found significant at the 95 percent or the 99 percent level. From the present study it was evident that full understanding of the physical linkage of SST over the Bay of Bengal with the ABMR is unclear. The SST over the Bay of Bengal resulted from the association with Sea Level Pressure (SLP) and surface wind. To examine the association between SLP and wind anomalies, it is necessary to study the Southern Oscillation Index (SOI). During the spring season, trade wind circulation over the south Indian Ocean is quite intense and plays a dominant role in the regulation of the cross-equatorial flow over the Bay of Bengal. However, more elaborative studies, especially on data analysis and numerical model simulation, are suggested for establishing a complete physical linkage of SST over the Bay of Bengal and ABMR.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:bay of bengal monsoon sea surface temperature rainfall
Date of Publication:01/01/2004