A study on raindrop size distribution variability in before and after landfall precipitations of tropical cyclones observed over southern India

. In stratiform rainfall, the melting layer is often visible in radar observations as an enhanced reflectivity band, the so-called bright band. Despite the ongoing debate on the exact microphysical processes taking place in the melting layer and on how they translate into radar measurements, both model simulations and observations indicate that the radar-measured melting layer properties are influenced by snow microphysical processes that take place above it. There is still, however, a lack of comprehensive observations to link the two. To advance our knowledge of precipitation formation in ice clouds and provide an additional constraint on the retrieval of ice cloud microphysical properties, we have investigated this link. This study is divided into two parts. Firstly, surface-based snowfall measurements are used to devise a method for classifying rimed and unrimed snow from X- and Ka-band Doppler radar observations. In the second part, this classification is used in combination with multi-frequency and dual-polarization radar observations to investigate the impact of precipitation intensity, aggregation, riming, and dendritic growth on melting layer properties. The radar-observed melting layer characteristics show strong dependence on precipitation intensity as well as detectable differences between unrimed and rimed snow. This study is based on the data collected during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) experiment, that took place in 2014 in Hyytiala, Finland.

https://acp.copernicus.org/articles/20/9547/2020/acp-20-9547-2020.pdf

Towards the connection between snow microphysics and melting layer: insights from multifrequency and dual-polarization radar observations during BAECC

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2017JD028205

Quantification of Observed Electrical Effect on the Raindrop Size Distribution in Tropical Clouds

The diurnal variation in the vertical structure of the raindrop size distribution (RSD) associated with stratiform rain at Kototabang, West Sumatra (0.20°S, 100.32°E), was investigated using micro rain radar (MRR) observations from January 2012 to August 2016. Along with the MRR data, the RSD from an optical disdrometer and vertical profile of precipitation from the Tropical Rainfall Measuring Mission were used to establish the microphysical characteristics of diurnal rainfall. Rainfall during 0000–0600 LST and 1800–2400 LST had a lower concentration of small drops and a higher concentration of large drops when compared to rainfall during the daytime (0600–1800 LST). The RSD stratified on the basis of rain rate (R) showed a lower total concentration of drops and higher mass-weighted mean diameter in 0000–0600 LST and 1800–2400 LST than in the daytime. During the daytime, the RSD is likely governed by a riming process that can be seen from a weak bright band (BB). On the other hand, during 0000–0600 LST and 1800–2400 LST, the BB was stronger and the rainfall was associated with a higher concentration of midsize and large drops, which could be attributed to more active aggregation right above the melting layer with minimal breakup. Diurnal variation in the vertical profile of RSD led to a different radar reflectivity (Z)-R relationship in the rain column, in which Z during the periods 0000–0600 LST and 1800–2400 LST was larger than at the other times, for the same R.

Diurnal Variation in the Vertical Profile of the Raindrop Size Distribution for Stratiform Rain as Inferred from Micro Rain Radar Observations in Sumatra

In radar observations of hydrometeors, the 0°C isotherm in the atmosphere (i.e., the freezing level) usually appears as a region of enhanced reflectivity. This region is known as the bright...

/pdf/relating-the-radar-bright-band-and-its-strength-to-surface-4j5bebtdt6.pdf

Relating the Radar Bright Band and Its Strength to Surface Rainfall Rate Using an Automated Approach

A study was carried out to investigate the rain drop size distribution (DSD) characteristics during strong bright band (SBB), weak bright band (WBB) and no bright band (NBB) regimes of stratiform rain by using an L-band wind profiler and Joss–Waldvogel disdrometer at Gadanki (13.5°N, 79.20°E), a tropical station in India. The stratiform events with SBB (bright band width >0.49 km) are associated with larger mean drops (Dm) at ground level compared with WBB and NBB situations. Different shapes of raindrop DSDs during these three situations suggest different microphysical processes involved in the evolution of rain DSDs. During SBB regimes, the raindrop spectrum, which is found to be governed predominantly by an aggregation process, is size controlled. On the other hand, during WBB regimes, the raindrop spectrum, which is found to be governed predominantly by a riming process, is number controlled. A new rain DSD parameterization scheme, P (Z, N0*), is proposed in the framework of multi-parameter radar observation. The considered parameters are radar reflectivity factor (Z) and normalized scale parameter (N0*). These two parameters are found to be mutually independent. Reasonable improvement in the estimation of rain intensity is observed by the developed P(Z, N0*) scheme compared with P(Z) and P(Z, Dm). The rain DSDs simulated by the developed P(Z, N0*) scheme are in good agreement with the observed spectrum.

https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/met.1551

A study of raindrop size distribution during stratiform rain and development of its parameterization scheme in the framework of multi-parameter observations

Mesoscale Convective Systems (MCSs) contribute a large proportion of the earth's precipitation and hence t heir study is important from climatological point of view. In this paper, s easonal and diurnal variation of MCSs parameters over southern peninsular India has been studied. MCSs data over land for a period of 13 yea rs (1998-2010) from Precipitation Measuring Mission (PMM) website of Utah University (www.trmm.chpc.utah.edu) have been utilized for this study. Distinct seasonal and diurnal variation of MCS parameters ar e observed over the study region. Number of occurrence and rainfall are maximum in June over southwest peninsular India and in October over sout heast peninsular India. MCSs are found to be more severe during pre-monsoon and least severe during south-west monsoon. Their severity is found to be maximum in the month of May by virtue of highest median value of 2 0dBZ echo-top height (14.8 km) associated with highest median value of C APE (1323 J/Kg). Convective fraction of rainfall is maximum in April and minimum in December. MCSs occurrence is found to be maximum in the late afternoon to evening and minimum in morning. They are found to be more intense during midday (10-14 hrs) and least intense during midnight (22-02 hrs). Diurnal cycle of convective fraction shows midday maximum and late night minimum.

http://jakraya.com/journal/download.php?file=6-ijeasArticle_1.pdf

Anal Chandra Sarma

Papers

A study of raindrop size distribution during stratiform rain and development of its parameterization scheme in the framework of multi-parameter observations

Seasonal and Diurnal Variation of Mesoscale Convective Systems Over Southern Peninsular India as Observed by TRMM Satellite