NOPR Collection:

Oceanic mixed layer variations during the movement of cyclone along symmetric tracks in the Indian Ocean

Thu, 01 Jun 2006 00:00:00 GMT

Title: Oceanic mixed layer variations during the movement of cyclone along symmetric tracks in the Indian Ocean Authors: Deo, A. A.; Ganer, D.W.; Salvekar, P. S. Abstract: The understanding of significant changes in the oceanic mixed layer is important for dynamical prediction of tropical cyclone. Present study aims at examining the variations in the upper ocean parameters during the movement of tropical cyclone in northern and southern Indian Ocean, by applying 1½ layer wind driven reduced gravity ocean model. Different idealized tracks in the Bay of Bengal and their mirror images in southern hemisphere are considered, The model produced mixed layer depth, temperature and currents are compared for northern and southern hemispheric cyclone cases. Also the effect of latitude for westward moving cyclones in both the hemisphere is investigated. For this, tracks in the Arabian Sea and their counter parts in the southern hemisphere are considered. The maximum cooling found in the wake of cyclone is of the order of 3 - 4°C, which is comparable with earlier studies and observations. This significant cooling can cause weakening of the storm. This can be useful for prediction especially in the event of a cyclonic storm heading towards land and likely to make land fall. Moreover it is also seen that the mixed layer is cooled more on the right (left) of the storm track in northern (southern) hemisphere. This cooling decreases for the storms translating along higher latitudes implying the sensitivity of the latitudinal location of the storm. Page(s): 111-122

Impact of satellite derived wind in mesoscale simulation of Orissa super cyclone

Thu, 01 Jun 2006 00:00:00 GMT

Title: Impact of satellite derived wind in mesoscale simulation of Orissa super cyclone Authors: Mandal, M.; Mohanty, U. C.; Das, A. K. Abstract: Prediction of track and intensity of tropical cyclones is one of the most challenging problems in numerical weather prediction (NWP). Providing reasonably accurate initial condition to tropical cyclone forecast models has always been a problem to numerical weather forecasters. Recent advancements in spatial resolution and radiometric sensitivity have significantly improved the accuracy and density of satellite derived wind. The objective of the present study is to examine the impact of satellite derived winds in improving model initial condition and hence in mesoscale simulation of cyclonic storm. In this study, PSU/NCAR mesoscale model MM5 is used to produce 5-day simulation of the super cyclone that crossed Orissa coast on 29 October 1999. Winds derived from QSCAT, SSM/I, MSMR and METEOSAT-5 satellites are used in preparation of high-resolution reanalysis (HRR) and improving model initial condition. The strength of the southwesterly wind (over ocean) converging to the storm is found to be stronger both in the HRR and improved model initial condition compared to that in the NCEP/NCAR reanalysis. The strength of the cyclonic vortex is also better represented in the HRR and improved model initial condition. Improvement in model initial condition has resulted in consistent and significant improvement (35% in average) in prediction of the track of the storm. Page(s): 161-173

A study on cyclone induced productivity in south-western Bay of Bengal during November-December 2000 using MODIS (SST and chlorophyll-a)

Thu, 01 Jun 2006 00:00:00 GMT

Title: A study on cyclone induced productivity in south-western Bay of Bengal during November-December 2000 using MODIS (SST and chlorophyll-a) Authors: Rao, K. H.; Smitha, A.; Ali, M. M. Abstract: MODIS (Moderate Resolution Imaging Spectroradiometer) on board TERRA weekly composite mean products of sea surface temperature (SST) and chlorophyll-a, and modeled ocean net primary productivity with a spatial resolution of 4.63 km and altimeter derived sea surface height (SSH) data are used to study the changes in the primary productivity (PP) induced by the November-December 2000 tropical cyclone in the Bay of Bengal. A maximum SST drop of 2ºC, a sea surface depression of 10 cm compared to the periphery, increase in chlorophyll-a by 1.5 mg/m³ and enhanced average mixed PP of 964 gC/m²/y were observed around 11.0ºN and 81.0ºE after the passage of the cyclonic storm. The enhanced PP after the passage of the cyclone supports the base of the pelagic marine food web, directly affecting the fishery productivity. Page(s): 153-160

Observations and numerical simulation of the sea and land breeze circulations along the west coast of India

Thu, 01 Jun 2006 00:00:00 GMT

Title: Observations and numerical simulation of the sea and land breeze circulations along the west coast of India Authors: Simpson, M. D.; S., Raman Abstract: Sea breeze circulation along the west coast of India during the Indian Ocean Experiment (1999) is investigated. Pilot balloon sounding data from Mumbai, Goa, and Trivandrum, India show a diurnal variation in wind direction caused by land and sea breeze circulations along the west coast of India. Rawinsonde wind profiles taken from R/V Sagar Kanya 130 km offshore from the west coast of India show the presence of sea and land breeze circulations. Infrared satellite images show the furthest extent of the sea breeze circulation over the Arabian Sea to be around 200 km. Constant level balloons released from Goa, India also showed the extent of the sea breeze over the ocean to be 200 km. A mesoscale numerical model was used to further investigate the sea breeze circulation and its horizontal extent over the ocean. Simulated cross sections along the west coast of India show the horizontal extent of the afternoon sea breeze over the ocean to vary from around 130 to 260 km. Vertical velocities of about 0.25 ms⁻¹ were simulated inland as the sea breeze interacted with the mountains along India’s west coast. Page(s): 139-152