Measurement and analysis of refractive index structure constant Cn2 profile over Delhi on diurnal and seasonal basis

jsfM;ksa rjax ds lapj.k dks izHkkfor djus esa jsfM;ks viorZdrk ,d egRoiw.kZ dkjd dk dk;Z djrh gSA jsfM;ks viorZdrk] ok;qeaMy dh HkkSfrd voLFkkvksa tSls & rkieku] nkc vkSj vknzZrk ij fuHkZj djrh gSA jsMkj vR;Ur NksVh vk—fr ds viorZukad fHkUurkvksa tks jsMkj ds rjax nS/;Z dh vk/kh gksrh gS] ds izfr laosnh gksrs gSA i'p izdh.kZu 'kfDr viorZukad fu;rkad Cn2 dh vk—fr ds ifjek.k ij fuHkZj djrh gSA vr% ekSle jsMkj] fo’k"k :i foaM izksQkbyj jsMkj ds fM+tkbu ds fy, fdlh LFkku ds Cn2 ds eku mi;ksxh gksrs gSA bl 'kks/k i= esa fnYyh ds Åij ds mijhru ok;qeaMy esa ok;qeaMyh; viorZukad fu;rkad Cn2 dh :ijs[kk nSfud ,oa _rqvksa ds vk/kkj ij rS;kj djus dh dksf’k’k dh xbZ gSA The radio refractivity is an important factor which effects radio wave propagation. Radio refractivity depends upon the physical states of atmosphere, i.e., its temperature, pressure and humidity. Radars are sensitive to refractive index irregularities on scale size equal to half wavelength of Radar. Backscattered power is dependent on the magnitude of refractive index structure constant Cn2. Hence Cn2values of a place are useful for designing weather radar specially wind profiler radars. This paper is an attempt to map the profile of refractive index structure constant Cn2 of atmosphere in the upper atmosphere, over Delhi on diurnal and seasonal basis.

How weather events modify aerosol particle size distributions in the Amazon boundary layer

This study evaluates the effect of weather events on the aerosol particle size distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines in situ measurements of PSD and remote sensing data of lightning density, brightness temperature, cloud top height, cloud liquid water, and rain rate and vertical velocity. Measurements were obtained by scanning mobility particle sizers (SMPSs), the new generation of GOES satellites (GOES-16), the SIPAM S-band radar and the LAP 3000 radar wind profiler recently installed at the ATTO-Campina site. The combined data allow exploring changes in PSD due to different meteorological processes. The average diurnal cycle shows a higher abundance of ultrafine particles (NUFP) in the early morning, which is coupled with relatively lower concentrations in Aitken (NAIT) and accumulation (NACC) mode particles. From the early morning to the middle of the afternoon, an inverse behavior is observed, where NUFP decreases and NAIT and NACC increase, reflecting a typical particle growth process. Composite figures show an increase of NUFP before, during and after lightning was detected by the satellite above ATTO. These findings strongly indicate a close relationship between vertical transport and deep convective clouds. Lightning density is connected to a large increase in NUFP, beginning approximately 100 min before the maximum lightning density and reaching peak values around 200 min later. In addition, the removal of NACC by convective transport was found. Both the increase in NUFP and the decrease in NACC appear in parallel with the increasing intensity of lightning activity. The NUFP increases exponentially with the thunderstorm intensity. In contrast, NAIT and NACC show a different behavior, decreasing from approximately 100 min before the maximum lightning activity and reaching a minimum at the time of maximum lightning activity. The effect of cloud top height, cloud liquid water and rain rate shows the same behavior, but with different patterns between seasons. The convective processes do not occur continually but are probably modulated by gravity waves in the range of 1 to 5 h, creating a complex mechanism of interaction with a succession of updrafts and downdrafts, clouds, and clear-sky situations. The radar wind profiler measured the vertical distribution of the vertical velocity. These profiles show that downdrafts are mainly located below 10 km, while aircraft observations during the ACRIDICON–CHUVA campaign had shown maximum concentrations of ultrafine particles mainly above 10 km. Our study opens new scientific questions to be evaluated in order to understand the intricate physical and chemical mechanisms involved in the production of new particles in Amazonia.

A Doppler radar study of convective draft lengths over Darwin, Australia

Data from an upward-pointing wind profiler radar pair at Darwin in tropical Australia are used to determine the characteristics of individual convective up- and downdrafts observed at the site. Drafts are identified as vertically contiguous regions of instantaneous upward or downward motion exceeding 0.2 ms−1. Most updrafts and downdrafts found are less than 2 km in vertical extent, and updrafts exceeding 5 km vertical length carry no more than 33% of the total upward mass flux. Updraft length correlates positively with rain rates, and on very high rain rates (greater than 20 mm/hr), average updraft lengths are ~5 km. Typical peak updraft velocities increase from ~2.5 ms−1 for the smallest to ~ 4 ms−1 for the largest drafts, while those for downdrafts remain ~ 2 ms−1 regardless of size. These results are broadly consistent with other numerical modeling studies, but contrast with the common view of deep convection as being dominated by continuous, deep drafts.

How weather events modify aerosol particle size distributions in the Amazon boundary layer

This study evaluates the effect of weather events on the aerosol particle size distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines in-situ measurements of PSD and remote sensing data of lightning density, brightness temperature, cloud top height, cloud liquid water, and rain rate and vertical velocity. Measurements were obtained by a scanning mobility particle sizers (SMPS), the new generation of GOES satellites (GOES-16), the SIPAM S-band radar, and the LAP 3000 radar wind profiler recently installed at the ATTO-Campina site. The combined data allow exploring changes in PSD due to different meteorological processes. The average diurnal cycle shows a higher abundance of ultrafine particles (NUFP) in the early morning, which is coupled with lower concentrations in Aitken (NAIT) and accumulation (NACC) mode particles. From the early morning to the middle of the afternoon, an inverse behavior is observed, where NUFP decreases and NAIT and NACC increase, reflecting a typical particle growth process. Composite figures show an increase of NUFP before, during, and after lightning was detected by the satellite above ATTO. These findings strongly indicate a close relationship between vertical transport and deep convective clouds. Lightning density is connected with a large increase in NUFP, beginning approximately 100 minutes before the maximum lightning density and reaching peak values around 200 minutes later. In addition, the removal of NACC by convective transport was found. Both the increase in NUFP and the decrease in NACC appear in parallel with the increasing intensity of lightning activity. The NUFP increases exponentially with the thunderstorm intensity. In contrast, NAIT and NACC show a different behavior, decreasing from approximately 100 minutes before the maximum lightning activity and reaching a minimum at the time of maximum lightning activity. The effect of cloud top height, cloud liquid water, and rain rate shows the same behavior, but with different patterns among seasons. The convective processes do not occur continually but are modulated by gravity waves in the range of 1 to 5 hours, creating a complex mechanism of interaction with a succession of updrafts and downdrafts, clouds and clear sky situations. The radar wind profiler measured the vertical distribution of the vertical velocity. These profiles show that downdrafts are mainly located below 10 km, while aircraft observations during the ACRIDICON-CHUVA campaign had shown maximum concentrations of ultrafine particles mainly above 10 km. Our study opens new scientific questions to be evaluated in order to understand the intricate physical and chemical mechanisms involved in the production of new particles in Amazonia.

Analysis of Extreme Meteorological Events in the Central Andes of Peru Using a Set of Specialized Instruments

A set of instruments to measure several physical, microphysical, and radiative properties of the atmosphere and clouds are essential to identify, understand and, subsequently, forecast and prevent the effects of extreme meteorological events, such as severe rainfall, hailstorms, frost events and high pollution events, that can occur with some regularity in the central Andes of Peru. However, like many other Latin American countries, Peru lacks an adequate network of meteorological stations to identify and analyze extreme meteorological events. To partially remedy this deficiency, the Geophysical Institute of Peru has installed a set of specialized sensors (LAMAR) on the Huancayo observatory (12.04° S, 75.32° W, 3350 m ASL), located in the Mantaro river basin, which is a part of the central Andes of Peru, especially in agricultural areas. LAMAR consists of a set of sensors that are used to measure the main atmosphere and soil variables located in a 30-meter-high tower. It also has a set of high-quality radiation sensors (BSRN station) that helps measure the components of short-wave (SW) (global, diffuse, direct and reflected) and long-wave (LW) (emitted and incident) irradiance mounted in a 6-meter-high tower. Moreover, to analyze the microphysics properties of clouds and rainfall, LAMAR includes a set of profiler radars: A Ka-band cloud profiler (MIRA-35c), a UHF wind profiler (CLAIRE), and a VHF wind profiler (BLTR), along with two disdrometers (PARSIVEL2) and two rain gauges pluviometers. The present study performs a detailed dynamic and energetic analysis of two extreme rainfall events, two intense frost events, and three high-pollution events occurring on the Huancayo observatory between 2018 and 2019. The results show that the rainfall events are similar to the 1965–2019 climatological 90th percentile of the daily accumulated rainfall. The results also highlighted the patterns of reflectivity in function of height for both events, which is measured by highlighting the presence of convective and stratiform rainfall types for both events. The first intense rainfall event was associated with strong easterly circulations at high levels of the atmosphere, and the second one was associated with the presence of strong westerly circulations and the absence of BH-NL system around the central Andes. The first frost event was mainly associated with continuous clear sky conditions in the few previous days, corresponding to a radiative frost event. The second one was mainly associated with the intrusion of cold surges from extra-tropical South America. For both events, the energy budget components were strong-lower in comparison to the mean monthly values during early morning hours. Finally, for the high pollution events, the study identified that the main source of aerosols were the forest fires that took place in Peru with certain contributions from the fires in the northern area of Bolivia.

Characteristics Analysis of Wind Components according to the Typhoon Track Influenced in the Korean Peninsula Using a Wind Profiler Radar

<p> </p><p> Typhoon is a tropical cyclone accompanied by strong wind and heavy precipitation. It induces high human and property damages depending on typhoon track. The typhoon influenced in the Korean Peninsula mainly passes through Jeju Island and the Southern costal area from northward the East China Sea. In this study, wind components analysis using a wind profiler radar close to the shoreline is conducted. The wind profiler radar observes the three-dimensional wind components for a fixed-point regardless of precipitation and provides high-resolution (10 min., 100 m) data for continuous analysis. The wind characteristics according to the typhoon track was investigated using the Boseong wind profiler radar (34.76 °N, 127.21 °E) located on the south coast in Korea.</p><p> Some cases were selected as typhoons that occurred in 2010 (Dianmu, Kompasu, Malou), 2011 (Meari, Muifa) and 2012 (Khanun). For the horizontal wind analysis, there were distributed the preprocessed zonal (U) and meridional (V) wind components with time. As a result, the shape of the scatter plot and their distribution characteristics were differently shown according to the typhoon track. Dianmu and Malou had circle-shape and distributed similarly over time, however Muifa, Meari, Kompasu and Khanun displayed the line-shape, relatively. Their differences were confirmed through the quadratic regression equations by each typhoon track. In addition, the amount of change in U and V was analyzed in time series.</p><p> These wind components analysis using ground-based observation data are expected to be applied for typhoon track analysis, prediction and natural disaster prevention.</p>

Technical note: First comparison of wind observations from ESA's satellite mission Aeolus and ground-based radar wind profiler network of China

Aeolus is the first satellite mission to directly observe wind profile information on a global scale. After implementing a set of bias corrections, the Aeolus data products went public on 12 May 2020. However, Aeolus wind products over China have thus far not been evaluated extensively by ground-based remote sensing measurements. In this study, the Mie-cloudy and Rayleigh-clear wind products from Aeolus measurements are validated against wind observations from the radar wind profiler (RWP) network in China. Based on the position of each RWP site relative to the closest Aeolus ground tracks, three matchup categories are proposed, and comparisons between Aeolus wind products and RWP wind observations are performed for each category separately. The performance of Mie-cloudy wind products does not change much between the three matchup categories. On the other hand, for Rayleigh-clear and RWP wind products, categories 1 and 2 are found to have much smaller differences compared with category 3. This could be due to the RWP site being sufficiently approximate to the Aeolus ground track for categories 1 and 2. In the vertical, the Aeolus wind products are similar to the RWP wind observations, except for the Rayleigh-clear winds in the height range of 0–1 km. The mean absolute normalized differences between the Mie-cloudy (Rayleigh-clear) and the RWP wind components are 3.06 (5.45), 2.79 (4.81), and 3.32 (5.72) m/s at all orbit times and ascending and descending Aeolus orbit times, respectively. This indicates that the wind products for ascending orbits are slightly superior to those for descending orbits, and the observation time has a minor effect on the comparison. From the perspective of spatial differences, the Aeolus Mie-cloudy winds are consistent with RWP winds in most of east China, except in coastal areas where the Aeolus Rayleigh-clear winds are more reliable. Overall, the correlation coefficient R between the Mie-cloudy (Rayleigh-clear) wind and RWP wind component observation is 0.94 (0.81), suggesting that Aeolus wind products are in good agreement with wind observations from the RWP network in China. The findings give us sufficient confidence in assimilating the newly released Aeolus wind products in operational weather forecasting in China.