Anomalous wind circulation over Taipei, Taiwan during the northern winter seasons of 2004 and 2005- A case study

This research reports, for the first time, an anomalous wind circulation over Taipei (Latitude 25.030N, Longitude 121.510E), Taiwan during the northern hemisphere winter season (December, January, and February) of years 2004 and 2005. The anomalous wind circulation of meridional winds, which showed southward directions during the winter seasons of 2004 and 2005 instead of northward winds, is noticed from one kilometer altitude range (lower troposphere) and that trend continued till around 20 km altitude range (lower stratosphere). To ascertain whether such a disturbed nature of wind pattern existed over nearby locations to Taipei, we have analyzed radiosonde-measured meridional and zonal winds over four nearby stations station to Taipei including, Roig, Xiamen, Minami and Fuzhou. Surprisingly, no anomalous wind behavior is seen except over Taipei during the northern winter seasons of 2004 and 2005. On the other hand, the European Centre for Medium-Range Weather Forecasts (ECMWF) model-predicted winds do not show any anomalous wind patterns over Taipei and other nearby stations, possibly due to the large averaging of internal variabilities of reanalysis databases. The plausible physical mechanisms of these disturbed meridional wind patterns are not understood at this juncture, but it is believed that local winds and atmospheric pollutants might have created an amicable environment as to provide such a disturbed meridional wind pattern over Taipei, Taiwan in the winter season of 2004 and 2005

Lower and middle atmospheric responses to the 22 July 2009 total solar eclipse

91-102In the present study, the effect of total solar eclipse, occurred on 22 July 2009, on water vapour in the troposphere, refractivity and temperature in the troposphere and the stratosphere using the observations available from COSMIC GPS RO, is reported. The investigation is extended to the entire middle atmosphere using SABER aboard TIMED satellite to study the response in the temperature and ozone. A significant enhancement in the water vapour and the refractivity in the lower and middle troposphere are noticed on the eclipse day when compared to non-eclipse days. Using the GPS RO observations, it is also found that the temperature responds differently at different altitudes, i.e. cooling in the troposphere and warming in the stratosphere. Similar features in temperature are also noticed in SABER observations below 40 km. Above 40 km altitude, cooling is observed up to an altitude of 70 km, therein again warming is noticed. An increase in ozone concentration is found throughout the middle atmosphere except near 30 km. Tropopause altitude is also observed to vary significantly during the solar eclipse with decrease (increase) in the altitude (temperature) of about 1-1.5 km (3-5 K). Large perturbations in the temperature, due to gravity waves in the stratosphere and the mesosphere, are noticed on the eclipse day and found westward propagating as expected. For the first time, evidences of solar eclipse in the entire lower and middle atmosphere is presented using ground based and satellite borne observations. </span

Investigating the effect of hygroscopicity of aerosols on optical profiles of PBL observed by dual-wavelength lidar

The light scattering and radiation properties of aerosols are mainly dominated by hygroscopicity. In this study, the relationship between the wavelength dependent ratio of lidar scattering signals (color ratio) and relative humidity and the application of the color ratio to identify the cloud base is examined

Investigating the effect of hygroscopicity of aerosols on optical profiles of PBL observed by dual-wavelength lidar

The light scattering and radiation properties of aerosols are mainly dominated by hygroscopicity. In this study, the relationship between the wavelength dependent ratio of lidar scattering signals (color ratio) and relative humidity and the application of the color ratio to identify the cloud base is examined

Investigation on The Interlink Between Optical Properties of Dusts Over Taiwan and Thar Desert, India Using CALIPSO Data

The optical properties (Angstrom exponent and depolarization) of aerosols are analyzed to characterize the dust particles at different altitudes of the atmosphere using the backscatter signal from the space borne Lidar (CALIPSO) over Asian region with emphasis on Taiwan and Indian regions. The physical and optical properties of dust particles are found different at wet and dry weather conditions. The size distribution of dust particles at different altitudes is estimated. Finally the correlation between the particle depolarization and the angstrom exponent of dust particles at different altitudes is analyzed and the possible reasons are discussed. Further, the spatial inhomogeneity in the correlation coefficient is noticed and the possible relation with regional weather conditions is discussed

Investigation on The Interlink Between Optical Properties of Dusts Over Taiwan and Thar Desert, India Using CALIPSO Data

The optical properties (Angstrom exponent and depolarization) of aerosols are analyzed to characterize the dust particles at different altitudes of the atmosphere using the backscatter signal from the space borne Lidar (CALIPSO) over Asian region with emphasis on Taiwan and Indian regions. The physical and optical properties of dust particles are found different at wet and dry weather conditions. The size distribution of dust particles at different altitudes is estimated. Finally the correlation between the particle depolarization and the angstrom exponent of dust particles at different altitudes is analyzed and the possible reasons are discussed. Further, the spatial inhomogeneity in the correlation coefficient is noticed and the possible relation with regional weather conditions is discussed

Sub-daily variations observed in Tropical Easterly Jet (TEJ) streams

To investigate the sub-daily variation in Tropical Easterly Jet (TEJ), a few special experiments have been conducted with mesosphere-stratosphere-troposphere (MST) radar located at Gadanki(13.5°N, 79.2°E) under Study on Atmospheric Forcing and Responses (SAFAR) campaign during 2008-2009. Large sub-daily changes in the TEJ characteristics are observed within a day in addition to day-to-day changes. Based on this observational study, three possible mechanisms for the sub-daily variations are proposed i.e., (1) motion of TEJ core, (2) large updrafts and downdrafts, and (3) strong wave activity. Interestingly, TEJ peak altitude is seen above the Cold Point Tropopause altitude for about 42% of the days

Intriguing aspects of the monsoon low-level jet over peninsular India revealed by high-resolution GPS radiosonde observations

The strong cross-equatorial flow in the lower troposphere, widely known as the monsoon low-level jet (MLLJ), plays an important role in the Indian summer monsoon (ISM) rainfall during June–September. Using high-resolution GPS radiosonde observations over Gadanki (13.5°N, 79.2°E), some new aspects of MLLJ have been reported. In the present study it is found that, on average, the MLLJ exists at 710 hPa over southeastern peninsular India, rather than at 850 hPa as reported by earlier studies. It is observed that the ECMWF Re-Analysis (ERA)-Interim data provide better results on the spatial, temporal, and vertical variation of MLLJ. Further, the characteristics of the MLLJ during the active and break spells of ISM are also investigated; higher MLLJ core height and intensity are found during active phases of the Indian monsoon. This study emphasizes the use of high-resolution measurements for studying monsoon dynamics in detail

Unusual enhancement in temperature and ozone vertical distribution in the lower stratosphere observed over Gadanki, India, following the 15 January 2010 annular eclipse

Extensive observations on various atmospheric parameters were carried out from Gadanki (13.48°N, 79.18°E), a tropical station in India, during the annular solar eclipse of 15 January 2010. In the present study, we report changes observed in temperature and ozone concentration in the lower stratosphere associated with the eclipse. Unusual enhancements in the temperature of 12.5 K and in ozone concentration of 5.5. mPa are observed around 21 km just after the eclipse. Plausible mechanisms for the observed eclipse effects are discussed using data of simultaneous vertical and horizontal winds collected through co-located MST radar observations. From the preliminary analysis, the temperature and ozone enhancements are attributed to large subsidence and horizontal advection, respectively

Characteristics of the Tropical Easterly Jet: long-term trends and their features during active and break monsoon phases

Using high-vertical resolution Indian mesosphere-stratosphere-troposphere (MST) radar and GPS sonde observations from Gadanki (13.5°N, 79.2°E), an attempt has been made for the first time to delineate the characteristics of Indian summer monsoon winds with special emphasis on the Tropical Easterly Jet stream (TEJ), its day-to-day, monthly, and interannual variability using observations available for more than a decade (1996-2008). For comparison, data available during 1996-2008 from routine radiosonde observations from nearby India Meteorological Department (IMD) observatory located at Chennai (13.0°N, 80.1°E) and National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets have been considered. Relatively poor vertical resolution data from IMD lead to underestimation of the jet characteristics like jet width, vertical shear above and below the jet, and the wind reversal height. Although reanalysis data sets represented well the spatial variability, they underestimate the peak zonal winds by about 5 m/s when compared to Indian MST radar and GPS sonde observations. Large day-to-day variability of TEJ characteristics (peak jet speed, jet height, jet width, zonal wind reversal height, and vertical shear of zonal wind) over Gadanki is noticed. No significant trend is observed in peak jet speed using reanalysis data sets either over Gadanki grid or over jet core region in Indian summer monsoon months. However, MST radar and GPS sonde observations show increasing trend (~1 m/s/yr) in peak jet speed particularly from the year 2000. Characteristics of the TEJ during active and break phases showed quite different features. Thus, statistics generated using the long-term database from Indian MST radar and GPS sonde provide valuable information for studying the TEJ characteristics and will be useful to incorporate in the future reanalysis data sets