Physical processes controlling the diurnal cycle of convective storms in the Western Ghats

Krishna, U. V. Murali; Das, Subrata Kumar; Deshpande, Sachin M.; Pandithurai, G.

doi:10.1038/s41598-021-93173-0

Cited by 20 publications

(9 citation statements)

References 62 publications

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“…Krishna et al. (2021) have recently showed that in the leeward side (a rain shadow region), the convection is dominated by the diurnal cycle of surface heating. All these supports the present findings in Figure 6 that storms associated with lightning have a larger propensity of high occurrence mostly over the leeward side of WG compared to the windward side.…”

Section: Resultsmentioning

confidence: 99%

“…From this it may be inferred that the higher (lower) percentages of intense convective cores are generally found in the regions of low (high) overall storm occurrence (see their Figure 2a). Krishna et al (2021) have recently showed that in the leeward side (a rain shadow region), the convection is dominated by the diurnal cycle of surface heating. All these supports the present findings in Figure 6 that storms associated with lightning have a larger propensity of high occurrence mostly over the leeward side of WG compared to the windward side.…”

Section: Spatial Distributionmentioning

confidence: 99%

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Relationship Between Convective Storm Properties and Lightning Over the Western Ghats

Utsav

Deshpande

Das

et al. 2022

Earth and Space Science

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X‐band radar observations are integrated with lightning location network observations to investigate the relationship between convective storm properties and lightning over the Western Ghats during a monsoon season (June–September 2014). Convective storms (cells) were identified using an objective‐tracking method and instantaneous lightning strikes within the radar domain were then linked with observed storms. This spatio‐temporal sampling of individual convective cells and lightning has facilitated process‐based study of electrified convection over the Ghats for the first time. Storm and lightning occurrences are typically high during monsoon onset and withdrawal months of June and September, respectively. A spatial correspondence between deep‐intense storms, lightning, and intense convective cores indicated presence of large hydrometeors in the mixed‐phase region of storm supported by strong updrafts and is essential for lightning. The large‐scale instability that peaked during afternoon hours was a key factor in the formation of deep‐intense storms and lightning. Results show that majority of lightning‐producing storms are located on the leeward side as opposed to the windward side. These storms have deeper top‐heights, larger areas and vertically integrated liquid, and an enhanced hail probability than those devoid of lightning. Warm season convection in the study area is accompanied by the preponderance of negative Cloud to Ground (−CG) flashes over positive Cloud to Ground (+CG) lightning. Storms with +CG features exhibited much higher (>2 times) vertical airmass flux in the mid‐troposphere (6–9 km) than storms without +CG features. Furthermore, for majority of +CG storms, intracloud flash occurrences increased significantly above the freezing level.

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Section: Resultsmentioning

confidence: 99%

Section: Spatial Distributionmentioning

confidence: 99%

Relationship Between Convective Storm Properties and Lightning Over the Western Ghats

Utsav

Deshpande

Das

et al. 2022

Earth and Space Science

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“…Based on the data collected at HACPL by the various in-situ instruments, some studies in the past performed to understand cloud-aerosol interaction over the Western Ghats (Anil Kumar et al, 2016;Buchunde et al, 2019;Das et al, 2017Das et al, , 2020Jayachandran et al, 2018;Konwar et al, 2010Konwar et al, , 2014Krishna et al, 2021;Kumar et al, 2022;Kumar & Silva, 2019;Leena et al, 2016Leena et al, , 2018Leena et al, , 2021Mukherjee et al, 2018;Singla et al, 2017;Sumesh et al, 2019Sumesh et al, , 2021Utsav et al, 2017;Varghese et al, 2021;. To study the diurnal variation of DSD, we use an impact-based disdrometer, i.e., Joss-Waldvogel Disdrometer (JWD) (Joss & Waldvogel, 1969) measurements during the Indian Summer Monsoon (ISM: June, July, August and September month) period between 2015 and 2019 at the HACPL, Mahabaleshwar, which is situated in the windward side of the Western Ghats in India.…”

Section: Joss-waldvogel Disdrometermentioning

confidence: 99%

Diurnal variation of rain drop size distribution over the Western Ghats in India

Kumar,

Srivas,

Chakravarty

et al. 2023

Preprint

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Joss-Waldvogel Disdrometer (JWD) measurements at the High-Altitude Cloud Physics Laboratory (HACPL: 17.56°N, 73.4°E, above 1373 m MSL), Mahabaleshwar were investigated for determining the diurnality of the drop size distribution (DSD) associated with the precipitation characteristics over the Western Ghats. Here, we examined the JWD data from 2015 to 2019 collected during the Indian Summer Monsoon (ISM) season. The number concentration of rain droplets of various diameters is considerably varying with the rain rate (R) and type of precipitating cloud. With increasing the value of R, rain droplets having larger diameter concentration significantly increase, and distribution tail moves to the biggest droplets. The average of reflectivity (Z), R, liquid water content (LWC), mass-weighted mean diameter (Dm), and normalized intercept parameter (log10Nw) have higher values from the heavy rainfall (Rhigh ≥10 mm/hr) in comparison to the low rainfall (Rlow < 10 mm/hr) for seasonal rainfall. The gamma distribution of DSD shows significant difference during the low and heavy precipitation on different time period (e.g. 00-06, 06-12, 12-18, 18-24 LST). The number of rain events contributing to the total accumulated rain varies with time. The maximum number of rain events occurred during 12-18 LST, with 23.6 % rain events of low rainfall and 4.9% of heavy rainfall. The bimodality is observed in the diurnal variation of Dm, R, and Z, with the largest peak recorded in the late afternoon (13-16 LST) and the second crest in the early morning hours (05 LST). At the same time, the log10Nw value drops down, indicating the lowest concentration of rain droplets. Several factors, like the land-sea breeze, complex mountainous terrain, and amount of surface reaching solar radiation may control the formation of precipitating clouds at the microphysical scale on the windward side of the Western Ghats, and may also responsible for the observed diurnality in DSD.

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“…The 0000 UTC soundings are used to classify the different phases of F. The 0000 UTC soundings are chosen for the following reasons. The peak of the diurnal cycle of rainfall over the Western Ghats is around 1030 UTC (1600 LST: (Flynn et al, 2017;Krishna et al, 2021)), thus, the 1200 UTC soundings, on most days, will reflect the conditions over the coast shortly after the peak rainfall events. Second, we believe that the nocturnal to early morning anomalous land/valley breeze is a key element in the offshore propagation of rainfall.…”

Section: Phases Of Fmentioning

confidence: 99%

Froude‐number‐based rainfall regimes over the Western Ghats mountains of India

Phadtare

Fletcher

Ross

et al. 2022

Quart J Royal Meteoro Soc

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Variations in the character of monsoonal rainfall over the Western Ghats region on the west coast of India are studied using radiosondes, satellite observations, and reanalysis products. Summer monsoon rainfall over this region occurs in alternate offshore and onshore phases. It is shown that these phases are controlled primarily by the strength of the low-level westerly jet. Thus, a classification based on the Froude number, F = U∕NH, of the onshore flow is proposed, where, H is the mountain height, U is the mean wind speed, and N is the mean Brunt-Väisäla frequency over depth H. At low F (< 0.5), onshore winds are weak and the diurnal thermal fluctuation over the orography is strong; the land-sea and mountain-valley circulations are enhanced, leading to a stronger diurnal control over the rainfall. A nocturnal offshore propagation of rainfall from the west coast is seen during this phase. Rainfall over the rainshadow region to the east of the Western Ghats also increases, due to a weaker lee effect, while it decreases over the Western Ghats, due to a greater blocking effect. At high F (> 1), orographic blocking of the low-level winds is weak. Thus, rainfall is enhanced over the Western Ghats and reduced over the rainshadow region due to a stronger lee effect. In this phase, the diurnal thermal fluctuation over the orography is weak. The bulk Richardson number is less than 1, suggesting a dominance of vertical wind shear over the buoyancy forces. The level of free convection and convective inhibition over the west coast are also very low. Hence, at high F, rainfall over the west coast results mainly from mechanical uplifting of the westerly winds by the Western Ghats, with no preference for a particular time of day. These findings will help in improving the representation of orographic effects and the diurnal cycle of rainfall in numerical models.

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Physical processes controlling the diurnal cycle of convective storms in the Western Ghats

Cited by 20 publications

References 62 publications

Relationship Between Convective Storm Properties and Lightning Over the Western Ghats

Relationship Between Convective Storm Properties and Lightning Over the Western Ghats

Diurnal variation of rain drop size distribution over the Western Ghats in India

Froude‐number‐based rainfall regimes over the Western Ghats mountains of India

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