Soumyajyoti Jana

Bio: Soumyajyoti Jana is an academic researcher from University of Calcutta. The author has contributed to research in topics: Boundary layer & Gravity wave. The author has an hindex of 7, co-authored 20 publications receiving 148 citations.

Prediction of convective rainfall using multi-technique observations

Abstract: Nowcasting of rain amount is extremely essential in various fields of life. In this paper, we have shown that monitoring of brightness temperature at 31.4 GHz, the frequency having strong absorption due to liquid water, can give an estimate of rain accumulation with a prediction efficiency of ∼ 80 % and a lead time of 75 minutes. It has also been observed that atmospheric electric field also shows definite changes before rain the magnitude of which can be related with the rainfall amount.

Convective rain study with radiometer, radar and electric field observations at a tropical location

Abstract: Characterization of convective rain at tropical station Kolkata, located near the land-ocean boundary, in the eastern part of India, has been made using observations from multi-frequency radiometer, micro rain radar, disdrometer and electric field monitor. Features of convective rain in respect of liquid water content, rain rate profile, and electric field variation have been identified. Multi-frequency radiometric brightness temperatures are used to nowcast impending rain events and rain fall amount.

Comparison between DSD parameters from GPM and Ground Based Disdrometer at Kolkata

Abstract: Precipitation is an important component in the water and energy cycle, playing an important role in many areas such as hydrology, meteorology and climatology. A long term and global data of raindrop size distribution (DSD) is required to understand the precipitation climatology and its role in climate change. The Global Precipitation Measurement Mission (GPM) can provide the parameters of the DSD globally [1]. The measurements of reflectivity (Z) profile by dual-frequency Precipitation Radar (DPR) of GPM satellite at Ku (13.6 GHz) and Ka-band (35.5 GHz) are used to retrieve drop size distribution on the ground for the present location Kolkata, India $(22^{\circ}34$’N, $88^{\circ}22$’E). An impact type Joss, Waldvogel disdrometer (JWD, Distromet RD-80), is operated at the Institute of Radio Physics and Electronics to measure rain DSDs at ground. The DSD from disdrometer has been used to calculate reflectivity at the two frequency of GPM. The reflectivities at ground from disdrometer and GPM are compared for five different rain rate (RR) classes namely:(i) 1 mm/$\mathrm{h}\lt$ RR $\lt =10$ mm/h, (ii) 10 mm/$\mathrm{h}\lt$ RR $\lt =20$ mm/h, (ii) 20 mm/$\mathrm{h}\lt$ RR $\lt =30$ mm/h, (iv) 30 mm/$\mathrm{h}\lt$ RR $\lt =40$ mm/h, and(v) 40 mm/$\mathrm{h}\lt$ RR $\lt =50$ mm/h. The Z values from GPM and disdrometer show good correspondence in the five rain rate classes. Figure 1(a) shows the Z values from GPM and disdrometer at the Ku-band for all the rain rate classes. The GPM data show somewhat underestimation of Z values from the disdrometer. DPR provided reflectivities at two frequencies are used to calculate the gamma parameters to retrieve the DSD from GPM observations. The DSDs from GPM and disdrometer show a good overall matching which is indicated in Figure 1(b) for the rain rate class 20 mm/$\mathrm{h}\lt$ RR $\lt =30$ mm/h. It can be noted that double peak in the disdrometer measured DSD is not shown in DSD from GPM (Figure 1(b)). The mass weighted mean drop diameter (Dm) and intercept parameters from GPM and disdrometer also show a good correlation for all the rain rate classes. The present technique will be used to obtain a three-dimensional picture of DSDs over the present location under varying raining condition. The comparison between GPM and disdrometer data shows the usefulness of GPM observations on global as well as regional scale.

Rain Radar Studies of Boundary Layer Dynamics at a Tropical Location

Abstract: Boundary layer dynamics play an important role in determining precipitation structure during convective processes. The radar reflectivity profiles which depend on the sixth moment of rain drop size distribution (DSD) can be employed to sense the precipitation processes. The height profiles of DSD significantly depend on the vertical wind velocity. The observations with a micro rain radar (MRR), an FMCW radar, over Kolkata, have been utilized to study the drop size distribution and its relationship with radar reflectivity at Ka-band. A sharp decrease of radar reflectivity in the height range 1–2 km corresponds to an increase of downdraft velocity observed around the same height range. This indicates that the increased downdraft causes breakup of rain drops into smaller sizes. The split in the Doppler spectrum, known as aliasing effect, is most prominent near the boundary layer height and has been employed to estimate downward wind velocity.

Land cover, land use changes and air pollution in Asia: a synthesis

Abstract: A better understanding of land cover/land use changes (LCLUC) and their interactions with the atmospheric environment is essential for the sustainable management of natural resources, environmental protection, air quality, agricultural planning and food security. The 15 papers published in this focus issue showcase a variety of studies relating to drivers and impacts of LCLUC and air pollution in different South/Southeast Asian (S/SEA) countries. This synthesis article, in addition to giving context to the articles in this focus issue, also reviews the broad linkages between population, LCLUC and air pollution. Additionally, we identify knowledge gaps and research priorities that are essential in addressing air pollution issues in the region. We conclude that for effective pollution mitigation in S/SEA countries, quantifying drivers, sources and impacts of pollution need a thorough data analysis through ground-based instrumentation, models and integrated research approaches. We also stress the need for the development of sustainable technologies and strengthening the scientific and resource management communities through capacity building and training activities to address air pollution issues in S/SEA countries.