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

BACKGROUND 
Vitiligo is an acquired primary, usually progressive, melanocytopenia of unknown aetiology clinically manifested by circumscribed achromic macules and histologically by degeneration and disappearance of melanocytes in involved skin. Childhood vitiligo deserves special attention as it has unique epidemiological features. We wanted to determine, compare and analyze the clinical and epidemiological features and autoimmune disease associations in childhood vitiligo and adult vitiligo. 
METHODS 
It was a prospective cross-sectional observational hospital-based clinical study conducted in a suburban medical college hospital over 20 months which involved 120 patients with vitiligo who were assessed using detailed history and clinical examination for demographic and clinical data. Relevant history and family history were noted. Investigations including complete hemogram, serum biochemistry profile, thyroid profile and fasting plasma glucose examination were performed in all patients. Data were collected, tabulated, and all statistical analysis was done by using SPSS trial version 25 and in MS Excel 2007. 
RESULTS 
The majority of patients were in the age group of 16-30 years. Among 60 patients, female preponderance was noted in the study with a percentage of 53.3 % followed by 46 % males in the childhood group. The prevalence of segmental vitiligo was more in children (30 %) than in adults (5 %) which was statistically significant (P= 0.000). In adults, there was a statistically significant higher prevalence (P=0.000) of mucosal vitiligo (30 %) than in children (3.35 %). On performing statistical analysis, thyroid dysfunction (P=0.00) and diabetes mellitus (P=0.01) were found to be significantly more prevalent in adults than in children. 
CONCLUSIONS 
This study provides clinical evidence that vitiligo at different ages has different characteristics mainly regarding an increased incidence of segmental vitiligo and a more common positive family history among children than adults. A higher prevalence of thyroid dysfunction and diabetes mellitus in adult vitiligo patients compared to children warrants prompt treatment in all detected cases to prevent long-term morbidity and complications.

Clinicoepidemiological Features of Childhood and Adult Vitiligo - A Cross- Sectional Observational Study

BACKGROUND 
Alopecia areata (AA) is a common, chronic, autoimmune, inflammatory disease that causes non scarring hair loss. Treatment of moderate to severe AA is challenging without a definitive cure. This study was undertaken to compare the efficacy of platelet rich plasma (PRP) - a novel procedural therapy, intralesional triamcinolone acetonide (ILS) and intralesional normal saline (NS) in moderate to severe AA. 
METHODS 
A total of 75 patients clinically diagnosed with Alopecia Areata were enrolled and the severity of the disease was assessed by SALT score. Twenty-five patients each in Group A, B and C were treated with PRP, ILS and NS respectively at monthly intervals for four sessions. Improvement in hair regrowth (based on reduction in SALT SCORE) and adverse effects were noted in all cases in each group at each session and one month after the final sitting. Statistical analysis was done using the student's t-test for quantitative values and the chi-square test for qualitative values. 
RESULTS 
Males outnumbered females with a percentage of 74.7, whereas females were 25.3 %. Male: female ratio of 2.9:1. Patchy type of AA was the most common clinical type observed (54.66 %), followed by sub totalis (14.66 %). Forty-eight cases (64 %) had a severity grade of S2 (26-50) followed by twenty-three cases (30 %) grade of S3 (51-75). After 20 weeks of treatment, the mean percentage of SALT score improvement with the highest efficacy was seen in the ILS group (63.15 %) followed by the PRP group (37.51 %). Improvement of hair regrowth with the excellent response (66 %) was achieved in ILS followed by 33 % in the PRP group, comparatively rapid reduction in SALT SCORE within four weeks was observed in the ILS group whereas gradual reduction in SALT SCORE was achieved in 8-12 weeks in PRP group. Relapse was seen in 21.7 % of patients in the ILS group and 1 (4.1 %) patient in the PRP group in the follow-up period of four months. No major adverse effects were seen in any of the groups. 
CONCLUSIONS 
Efficacy of ILS was more significant than PRP and Placebo but with a higher recurrence rate. Both treatments were extremely safe, with no significant adverse effects.

Randomized Study to Evaluate the Efficacy of Platelet Rich Plasma, Intralesional Triamcinolone Acetonide and Intralesional Normal Saline in Moderate to Severe Alopecia Areata

T. Narayana Rao

Papers

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

Clinicoepidemiological Features of Childhood and Adult Vitiligo - A Cross- Sectional Observational Study

Randomized Study to Evaluate the Efficacy of Platelet Rich Plasma, Intralesional Triamcinolone Acetonide and Intralesional Normal Saline in Moderate to Severe Alopecia Areata