S K Deb
Articles written in Journal of Earth System Science
Volume 117 Issue 5 October 2008 pp 589-602
The summer monsoon season of the year 2006 was highlighted by an unprecedented number of monsoon lows over the central and the western parts of India,particularly giving widespread rainfall over Gujarat and Rajasthan.Ahmedabad had received 540.2 mm of rainfall in the month of August 2006 against the climatological mean of 219.8 mm.The two spells of very heavy rainfall of 108.4 mm and 97.7 mm were recorded on 8 and 12 August 2006 respectively.Due to meteorological complexities involved in replicating the rainfall occurrences over a region,the Weather Research and Forecast (WRF –ARW version)modeling system with two different cumulus schemes in a nested con ﬁguration is chosen for simulating these events.The spatial distributions of large-scale circulation and moisture ﬁelds have been simulated reasonably well in this model,though there are some spatial biases in the simulated rainfall pattern.The rainfall amount over Ahmedabad has been underestimated by both the cumulus parameterization schemes.The quantitative validation of the simulated rainfall is done by calculating the categorical skill scores like frequency bias,threat scores (TS)and equitable threat scores (ETS).In this case the KF scheme has outperformed the GD scheme for the low precipitation threshold.
Volume 122 Issue 4 August 2013 pp 935-946
Till now low-level winds were retrieved using Kalpana-1 infrared (IR) images only. In this paper, an attempt has been made to retrieve low-level cloud motion vectors using Kalpana-1 visible (VIS) images at every half an hour. The VIS channel provides better detection of low level clouds, which remain obscure in thermal IR images due to poor thermal contrast. The tracers are taken to be 15 × 15 pixel templates and hence each wind corresponds to about 120km × 120km at sub-satellite point. Multiplet based wind retrieval technique is followed for VIS wind derivation. However, for height assignment of VIS winds, collocated IR image is used. Due to better contrast between cloud and ocean surface, the low level atmospheric flow is captured better as compared to IR winds. The validation of the derived VIS winds is done with Global Forecast System (GFS) model winds and Oceansat-II scatterometer (OSCAT) winds.