Meetings: Documents

The Seasonal Water Cycle over the India Subcontinent Indicated in the Correlated Analysis of Aquarius, GRACE and River Discharge Data
[18-Dec-14] Yueh, S., Tang, W., Fore, A., Hayashi, A., Bindlish, R., Lee, T., and Jackson, T.J.
Presented at the 2014 AGU Fall Meeting
Aquarius is a combined passive/active L-band microwave instrument. Its data have been used to retrieve the sea surface salinity (SSS) using the Combined Active and Passive (CAP) algorithm with an accuracy of about 0.1 to 0.2 psu Root-Mean-Square between 40 degrees N and 40 degrees S. In addition to the salinity product, Aquarius radiometer data have been used to produce the surface soil moisture globally. We find that the change of soil moisture over the India subcontinent clearly correlates with the timing of India Monsoon, which produces significant precipitation between June and September, and is consistent with the total land mass change derived from the GRACE mission data. We analyzed the time series of Aquarius soil moisture over the India subcontinent, Ganges river discharge and Aquarius surface salinity in the Bay of Bengal (BOB). There is excellent correlation between the river discharge and soil moisture throughout all seasons. However the change of surface salinity in the BOB seems to fall behind the change of soil moisture and river discharge by about 2 months before the monsoon season starts in June. This suggests that lighter precipitation before June does not have immediate impact on the surface salinity in the BOB. Once the heavier precipitation starts in June, the surface salinity in the BOB shows a rapid drop and the river discharge continues to rise until September when the monsoon season ends. We also compared the time series of Aquarius surface salinity in the BOB with the ARGO-gridded data produced by the Asia-Pacific Data-Research Center (APDRC). The comparison suggests that the Aquarius surface salinity in general agrees with the APDRC to within about 0.5 psu off the monsoon season, while during the monsoon season the Aquarius surface salinity tends to be below the APDRC by 1 to 3 psu. Our correlative analysis indicates that the larger discrepancy in August and September is likely due to the surface stratification resulting from rain or river discharge, while the evaporation appears to dominate the change of surface salinity from March to May.