New Characteristics of the Tropical Tropopause Revealed by CHAMP/GPS Measurements

Ratnam, M. Venkat; Tsuda, Toshitaka; Shiotani, Masato; Fujiwara, Masatomo

doi:10.2151/sola.2005-048

Cited by 23 publications

(25 citation statements)

References 22 publications

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“…2c and a small black circle shows the TC Nargis centre observed on 28 April 2008. An interesting feature to be noticed is the enhancement of CPH around 25 • N over the Indian region more than equatorial latitudes, which are well reported earlier (Venkat Ratnam et al, 2005). This feature is commonly observed over the Indian region.…”

Section: Classification Of the Tcssupporting

confidence: 85%

Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

Babu

Ratnam

Basha³

et al. 2015

Atmos. Chem. Phys.

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Abstract. Tropical cyclones (TCs) are deep convective synoptic-scale systems that play an important role in modifying the thermal structure, tropical tropopause parameters and hence also modify stratosphere-troposphere exchange (STE) processes. In the present study, high vertical resolution and high accuracy measurements from COSMIC Global Positioning System (GPS) radio occultation (RO) measurements are used to investigate and quantify the effect of tropical cyclones that occurred over Bay of Bengal and Arabian Sea in the last decade on the tropical tropopause parameters. The tropopause parameters include cold-point tropopause altitude (CPH) and temperature (CPT), lapse-rate tropopause altitude (LRH) and temperature (LRT) and the thickness of the tropical tropopause layer (TTL), that is defined as the layer between convective outflow level (COH) and CPH, obtained from GPS RO data. From all the TC events, we generate the mean cyclone-centred composite structure for the tropopause parameters and removed it from the climatological mean obtained from averaging the GPS RO data from 2002 to 2013. Since the TCs include eye, eye walls and deep convective bands, we obtained the tropopause parameters based on radial distance from the cyclone eye. In general, decrease in the CPH in the eye is noticed as expected. However, as the distance from the cyclone eye increases by 300, 400, and 500 km, an enhancement in CPH (CPT) and LRH (LRT) is observed. Lowering of CPH (0.6 km) and LRH (0.4 km) values with coldest CPT and LRT (2-3 K) within a 500 km radius of the TC centre is noticed. Higher (2 km) COH leading to the lowering of TTL thickness (2-3 km) is clearly observed. There are multiple tropopause structures in the profiles of temperature obtained within 100 km from the centre of the TC. These changes in the tropopause parameters are expected to influence the water vapour transport from the troposphere to the lower stratosphere, and ozone from the lower stratosphere to the upper troposphere, hence influencing STE processes.

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Section: Classification Of the Tcssupporting

confidence: 85%

Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

Babu

Ratnam

Basha³

et al. 2015

Atmos. Chem. Phys.

View full text Add to dashboard Cite

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“…• C. The mean value of tropopause height is found to be 17.3 km that is well in the range of earlier observations (Venkat Ratnam et al 2005). In 90% of the observations tropopause height is in the range of 16-19 km.…”

Section: Tropopause Heightsupporting

confidence: 82%

Atmospheric phenomena deduced from radiosonde and GPS occultation measurements for various application related studies

2009

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The tropopause height and tropopause temperature are sensitive to temperature changes in troposphere and stratosphere. These are the measures of global climatic variability. Atmospheric profiles of temperature, refractivity and water vapour are always needed for communication, navigation and atmospheric modeling studies. The tropopause characteristics over the Indian region have been studied using radio occultation measurements (CHAMP) on the basis of cold point criterion. Tropopause height shows large variation in the latitude range ∼ 30• -40• N during winter. Tropopause temperature less than −82• C, assumed to facilitate troposphere to stratosphere air transport, is observed at a number of tropical Indian locations and no seasonal pattern is observed in its occurrence. The bias in temperature and refractivity deduced from radiosonde and radio occultation measurements is also presented.

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“…These results are also consistent with earlier reports over other regions at tropical latitude (Newell et al, 1969;Reed and Vlcek, 1969;Reid and Gage, 1996;Seidel et al, 2001) in which it was attributed to the annual modulation of the Hadley cell. Thus, INSAT-3D data can be effectively utilised to investigate the tropopause characteristics to verify the new features reported in Venkat Ratnam et al (2005), but with a known caution of overestimation of T by 2-3 K. As the data from INSAT-3D are available for almost every hour, they are very useful for investigating stratosphere-troposphere exchange (STE) process occurring at subdaily scales. …”

Section: Consistency Check Of T Measurements Of Insat-3d In the Utls mentioning

confidence: 99%

Validation of INSAT-3D sounder data with in situ measurements and other similar satellite observations over India

2016

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Abstract. To date, several satellites measurements are available which can provide profiles of temperature and water vapour with reasonable accuracies. However, the temporal resolution has remained poor, particularly over the tropics, as most of them are polar orbiting. At this juncture, the launch of INSAT-3D (Indian National Satellite System) by the Indian Space Research Organization (ISRO) on 26 July 2013 carrying a multi-spectral imager covering visible to longwave infrared made it possible to obtain profiles of temperature and water vapour over India with higher temporal and vertical resolutions and altitude coverage, besides other parameters. The initial validation of INSAT-3D data is made with the high temporal (3 h) resolution radiosonde observations launched over Gadanki (13.5 • N, 79.2 • E) during a special campaign and routine evening soundings obtained at 12:00 UTC (17:30 LT). We also compared INSAT-3D data with the radiosonde observations obtained from 34 India Meteorological Department stations. Comparisons were also made over India with data from other satellites like AIRS, MLS and SAPHIR and from ERA-Interim and NCEP reanalysis data sets. INSAT-3D is able to show better coverage over India with high spatial and temporal resolutions as expected. Good correlation in temperature between INSAT-3D and in situ measurements is noticed except in the upper tropospheric and lower stratospheric regions (positive bias of 2-3 K). There is a mean dry bias of 20-30 % in the water vapour mixing ratio. Similar biases are noticed when compared to other satellites and reanalysis data sets. INSAT-3D shows a large positive bias in temperature above 25 • N in the lower troposphere. Thus, caution is advised when using these data for tropospheric studies. Finally it is concluded that temperature data from INSAT-3D are of high quality and can be directly assimilated for better forecasts over India.

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New Characteristics of the Tropical Tropopause Revealed by CHAMP/GPS Measurements

Cited by 23 publications

References 22 publications

Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

Atmospheric phenomena deduced from radiosonde and GPS occultation measurements for various application related studies

Validation of INSAT-3D sounder data with in situ measurements and other similar satellite observations over India

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