A study of evening convective clouds over Kochi and neighbourhood

Radar echoes of 0900 and 1100 UTC over Kochi and 200 km around were studied from 1996 to 1999 along with SST of southeast Arabian Sea and Kochi. The following results are obtained : Monsoon convective cloud tops were lower than Pre-monsoon and Post-monsoon convective cloud tops. (ii) In the mean, monsoon cloud tops gradually increased from 1996 to 1998 and then decreased. (iii) Very large convective activity existed during August 1997 to June 1998 compared to other periods of this study. Seasonally the higher the SST, the higher is convective cloud top. (v) Interannually, large positive SST anomaly coincided with high convective activity and this may be related to then prevailing El Nino.

Rain drop size distribution characteristics of cyclonic and north east monsoon thunderstorm precipitating clouds observed over Kadapa (14.47°N, 78.82°E), Tropical semi-arid region of India

Hkkjr ds vkU/kz izns’k jkT; ds v/kZ'kq"d HkwHkkx] dM+ik ¼14-47 fMxzh m-] 78-82 fMxzh iw- ½ esa yxk, x, d.k ds vkdkj vkSj osx ¼ikjohosy½ okys fMLMªksehVj l ‘ty’ pØokr ls mRiUu o"kZ.k es?kksa ¼07 uoEcj 2010½ rFkk mRrj iwoZ ¼,u- bZ-½ ekulwu xtZ okys rwQku ds o"kZ.k es?kksa ¼16 uoEcj 2010½ ds cw¡n ds vkdkj ds forj.kksa ¼vkj- ,l- Mh-½ dks ekik x;k gSA izs{k.kkRed ifj.kkeksa ls gesa ;g irk pyk gS fd pØokr dh otg ls mRiUu o"kZ.k es?kksa esa laoguh o"kZ.k izcy jgkA tcfd mRrj iwoZ ekulwu ds ekeys esa xtZ okys rwQku o"kZ.k laoguh es?k ds Hkkx Lrjh es?kksa dh rwyuk esa vf/kd gSaA pØokr ls mRiUu o"kZ.k] mRrj iwoZ ekulwu o"kZ.k dh rqyuk esa Lrjh {ks= ¼laoguh {ks=½ esa NksVh cw¡nksa ¼NksVh vkSj e/;e vkdkj dh cw¡nksa½ ls laca/k gSA Lrjh vkSj laoguh es?k {ks=ksa esa mRrj iwoZ ekulwu o"kZ.k dh rwyuk esa vkSlr nzO;eku Hkkfjr O;kl] pØokr ls mRiUu o"kZ.k dk Dm de gSA o"kkZ dh cw¡nksa ds vkdkj dk izs{k.k pØokrh; vkSj mRrj iwoZ ekulwu xtZ ds lkFk rwQkuksa ds o"kZ.k es?kksa esa vyx rjg dh fHkUurk ns[kh xbZ gSA Raindrop size distributions (RSD) of “JAL” Cyclone induced precipitating clouds (7 Nov. 2010) and North- East (NE) monsoon thunderstorm precipitating clouds (16 November 2010) were measured with a Particle Size and Velocity (PARSIVEL) disdrometer deployed at Kadapa (14.47°N; 78.82°E), a semiarid continental site in Andhra Pradesh state, India. From the observational results we find that stratiform precipitation is predominant than convective precipitation in cyclone induced precipitation clouds. Where as in the case of NE monsoon thunderstorm precipitation convective cloud fraction is more than stratiform clouds. The cyclone induced precipitation is associated with higher concentration of small drops (small and middrops) in stratiform region (convective region) than NE monsoon precipitation. The average mass weighted diameter, Dm of cyclone induced precipitation is less than the NE monsoon precipitation both in stratiform and convective cloud regions. The observed RSD are found distinctly vary from cyclonic and NE monsoon thunderstorm precipitating clouds.

Impacts of long-range-transported mineral dust on summertime convective cloud and precipitation: a case study over the Taiwan region

As one of the most abundant atmospheric aerosols and effective ice nuclei, mineral dust affects clouds and precipitation in the Earth system. Here numerical experiments are carried out to investigate the impacts of dust aerosols on summertime convective clouds and precipitation over the mountainous region of Taiwan by acting as ice-nucleating particles. We run the Weather Research and Forecasting model (WRF) with the Morrison two-moment and spectral-bin microphysics (SBM) schemes at 3 km resolution, using dust number concentrations from a global chemical transport model (GEOS-Chem-APM). The case study indicates that the long-range-transported mineral dust, with relatively low number concentrations, can notably affect the properties of convective clouds (ice and liquid water contents, cloud top height, and cloud coverage) and precipitation (spatial pattern and intensity). The effects of dust are evident during strong convective periods, with significantly increased ice water contents in the mixed-phase regime via the enhanced heterogeneous freezing. With both the Morrison and SBM schemes, we see the invigoration effects of dust aerosols on the convective intensity through enhanced condensation and deposition latent heating. The low-altitude dust particles are uplifted to the freezing level by updrafts, which, in turn, enhance the convective cloud development through immersion freezing and convective invigoration. Compared to the Morrison scheme, the SBM scheme predicts more realistic precipitation and different invigoration effects of dust. The differences are partially attributed to the saturation adjustment approach utilized in the bulk scheme, which leads to a stronger enhancement of condensation at midlatitudes to low altitudes and a weaker deposition increase at the upper level.

Aerosol-cloud-turbulence interactions in well-coupled Arctic boundary layers over open water

Late springtime Arctic mixed-phase convective clouds over open water in the Fram Strait as observed during the recent ACLOUD field campaign are simulated at turbulence-resolving resolutions. The main research objective is to gain more insight into the coupling of these cloud layers to the surface, and into the role played by interactions between aerosol, hydrometeors and turbulence in this process. A composite case is constructed based on data collected by two research aircraft on 18 June 2017. The boundary conditions and large-scale forcings are based on weather model analyses, yielding a simulation that freely equilibrates towards the observed thermodynamic state. The results are evaluated against a variety of independent aircraft measurements. The observed cloud macro- and microphysical structure is well reproduced, consisting of a stratiform cloud layer in mixed-phase fed by surface-driven convective transport in predominantly liquid phase. Comparison to noseboom turbulence measurements suggests that the simulated cloud-surface coupling is realistic. A joint-pdf analysis of relevant state variables is conducted, suggesting that locations where the mixed-phase cloud layer is strongly coupled to the surface by convective updrafts act as hot-spots for invigorated interactions between turbulence, clouds and aerosol. A mixing-line analysis reveals that the turbulent mixing is similar to warm convective cloud regimes, but is accompanied by hydrometeor transitions that are unique for mixed-phase cloud systems. Distinct fingerprints in the joint-pdf diagrams also explain i) the typical ring-like shape of ice mass in the outflow cloud deck, ii) its slightly elevated buoyancy, and iii) an associated local minimum in CCN.

Utilization of Red-Green-Blue (RGB) modification composite for nighttime convective cloud monitoring over North Sumatra region

Located between the Indian Ocean and the Malacca Strait, also the presence of the Bukit Barisan Mountains cause high convective activity in the North Sumatra region. The Himawari-8 satellite has 16 atmospheric observation channels that allow for observations of the convective system growth phase. The Red-Green-Blue (RGB) composite method is used to display a variety of satellite image composite information. The nocturnal convective system that often forms in the coastal areas of Sumatra causes heavy rains. A nocturnal convective system observation method is needed to publish early warning information on extreme weather. This research was conducted to observe the nocturnal convective system during heavy rain events in the North Sumatra region using a modification of RGB composite. This research used the Himawari-8 satellite data, Coloumn Max (CMAX) products of Medan weather radar data, and Global Satellite Mapping of Precipitation (GSMaP) rainfall estimation data. Comparison of RGB modified products with Night Microphysics RGB products and CMAX weather radar products, as well as time-series rainfall analysis. The results showed that the RGB modification product could capture the beginning of the convective system's growth, development, and spatial movement. The convective cloud distribution pattern corresponds to the area of heavy rain. There is a slight difference in cloud growth area between the satellite and radar products indicated the parallax error from the satellite image.

Spatial fraction verification of high resolution model

Fraction Skill Score (FSS) is one of spatial verification method to evaluate model performance on spatial scale variations. The method was applied to assess the Weather Research and Forecasting (WRF) model using 2 km (MODEL2KM) and 6 km (MODEL6KM) grid size. Cloud Top Temperature (CTT) data from Himawari-8 satellite was utilised as a ground truth data. This study aims to evaluate the model performance by FSS with absolute and percentile treshold on convective cloud simulation for three heavy rain events. The threshold considers the evaluation of absolute and percentile aspect. The result shows that there is no significant change in the FSS value for resolution increase of MODEL2KM compared to MODEL6KM. Also, the events of heavy rain having a lower CTT generate a higher FSS value for absolute threshold. Whilst, the percentile threshold for three cases have a greater FSS value, though it cannot provide the information of CTT absolute temperature value.

An Assessment of Convective Initiation Nowcasting Algorithm within 0-60 Minutes using Himawari-8 Satellite

Convective cloud monitoring since its growth stage primarily related to location and time of the first convective cloud initiated, called convective initiation (CI), could be the primary key in providing an earlier heavy rainfall event prediction. This study aimed to assess the accuracy and lead time of CI nowcasting using Satellite Convection Analysis and Tracking (SATCAST) algorithm in predicting the CI event within 0-60 minutes over Surabaya and surrounding area using Himawari-8 satellite during June-July-August (JJA) period in 2018. Three main processes used in this study were cloud masking, cloud object tracking, and CI nowcasting. Twelve interest fields were utilized as predictors based on six bands of Himawari-8 satellite, which represented cloud physics attributes such as cloud-top height, glaciation, or cooling rate. The verification was conducted by comparing CI prediction to CI location and time based on Surabaya weather radar within the next 0-60 minutes. The algorithm resulted that the prediction could achieve 87.3% of accuracy from the 3449 cloud objects. The prediction had POD, FAR, and CSI scores of 57.1%, 52.2%, and 35.2%, respectively. The 32.3 minutes of averaged lead time prediction indicated that CI nowcasting could detect growing cumulus about 30 minutes prior to the CI event.