scholarly journals Characterizing Extratropical Tropopause Bimodality and its Relationship to the Occurrence of Double Tropopauses Using COSMIC GPS Radio Occultation Observations

2020 ◽  
Vol 12 (7) ◽  
pp. 1109
Author(s):  
Benjamin Johnston ◽  
Feiqin Xie
Keyword(s):  
Radio Occultation ◽  
Asian Summer Monsoon ◽  
Local Maximum ◽  
Bimodal Distribution ◽  
Lapse Rate ◽  
Height Distribution ◽  
Gps Radio Occultation ◽  
Tropical Tropopause ◽  
Northern Edge ◽  
Extratropical Tropopause

Lapse rate tropopause (LRT) heights in the extratropics have been shown to display a bimodal distribution, with one modal maxima above 15 km (typical of the tropical tropopause) and the other below 13 km (typical of the extratropical tropopause). The climatology of the tropopause is studied by characterizing tropopause bimodality and how it relates to the occurrence of double tropopauses (DTs). LRT heights are derived from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS Radio Occultation temperature profiles from 2006 to 2017. Tropopause bimodality occurs most frequently within a subtropical band (20°–40°) in both hemispheres. A distinct seasonality is observed as bimodality occurs most frequently in winter except for another local maximum along the northern edge of the Asian summer monsoon. The regions with a bimodal height distribution nearly overlap the regions that experience a high frequency of DTs. DTs occur most frequently in winter (50%–70% of the time) along the poleward edge of the bimodal band, and most LRT heights are within the extratropical mode (>80%), whereas DT occurrence decreases quickly toward the equatorward edge (<20%) along with fewer LRT heights in the extratropical mode (<50%). These results indicate that LRT height bimodality occurs along the equatorward edge due to the occurrences of double tropopauses, while the poleward edge is due to single tropopause profiles that are more tropical in nature.

scholarly journals Characteristics of tropopause parameters as observed with GPS radio occultation

2014 ◽  
Vol 7 (11) ◽  
pp. 3947-3958 ◽  
Author(s):  
T. Rieckh ◽  
B. Scherllin-Pirscher ◽  
F. Ladstädter ◽  
U. Foelsche
Keyword(s):  
Annual Cycle ◽  
Radio Occultation ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Lapse Rate ◽  
Quasi Biennial Oscillation ◽  
Gps Radio Occultation ◽  
Statistical Measures ◽  
The Mean ◽  
Individual Profiles

Abstract. Characteristics of the lapse rate tropopause are analyzed globally for tropopause altitude and temperature using global positioning system (GPS) radio occultation (RO) data from late 2001 to the end of 2013. RO profiles feature high vertical resolution and excellent quality in the upper troposphere and lower stratosphere, which are key factors for tropopause determination, including multiple ones. RO data provide measurements globally and allow examination of both temporal and spatial tropopause characteristics based entirely on observational measurements. To investigate latitudinal and longitudinal tropopause characteristics, the mean annual cycle, and inter-annual variability, we use tropopauses from individual profiles as well as their statistical measures for zonal bands and 5° × 10° bins. The latitudinal structure of first tropopauses shows the well-known distribution with high (cold) tropical tropopauses and low (warm) extra-tropical tropopauses. In the transition zones (20 to 40° N/S), individual profiles reveal varying tropopause altitudes from less than 7 km to more than 17 km due to variability in the subtropical tropopause break. In this region, we also find multiple tropopauses throughout the year. Longitudinal variability is strongest at northern hemispheric mid latitudes and in the Asian monsoon region. The mean annual cycle features changes in amplitude and phase, depending on latitude. This is caused by different underlying physical processes (such as the Brewer–Dobson circulation – BDC) and atmospheric dynamics (such as the strong polar vortex in the southern hemispheric winter). Inter-annual anomalies of tropopause parameters show signatures of El Niño–Southern Oscillation (ENSO), the quasi–biennial oscillation (QBO), and the varying strength of the polar vortex, including sudden stratospheric warming (SSW) events. These results are in good agreement with previous studies and underpin the high utility of the entire RO record for investigating latitudinal, longitudinal, and temporal tropopause characteristics globally.

scholarly journals Tropical tropopause parameters derived from GPS radio occultation measurements with CHAMP

2004 ◽  
Vol 109 (D13) ◽  
pp. n/a-n/a ◽  
Author(s):  
T. Schmidt ◽  
J. Wickert ◽  
G. Beyerle ◽  
C. Reigber
Keyword(s):  
Radio Occultation ◽  
Gps Radio Occultation ◽  
Tropical Tropopause

scholarly journals Characteristics of the tropical tropopause inversion layer using high-resolution temperature profiles retrieved from COSMIC GNSS Radio Occultation

2018 ◽  
Author(s):  
Noersomadi Noersomadi ◽  
Toshitaka Tsuda ◽  
Masatomo Fujiwara
Keyword(s):  
Temperature Gradient ◽  
Radio Occultation ◽  
Deep Convection ◽  
Inversion Layer ◽  
Large Change ◽  
Static Stability ◽  
Lapse Rate ◽  
Temperature Profiles ◽  
Tropical Tropopause ◽  
The Tropics

Abstract. Using COSMIC GNSS Radio Occultation (RO) observations from January 2007 to December 2016, we retrieved temperature profiles with 0.1 km vertical resolution in the upper troposphere and lower stratosphere (UTLS). We investigated the global distribution of static stability (N2) and the characteristics of the tropopause inversion layer (TIL) in the tropics, where a large change in temperature gradient occurs associated with sharp variations of N2. We show the variations of the mean N2 profiles in conventional height coordinates as well as in coordinates relative to both the Lapse Rate Tropopause (LRT) and the Cold Point Tropopause (CPT). When the N2 profiles are averaged relative to CPT height, there is a very thin ( +0.5 K) in the PO, warmer SSTs in the MC and PO produce more active deep convection that tends to force the air upward to the tropopause layer and increase the temperature gradient there. The intra-seasonal variation in S-ab* during slow and fast episodes of the Madden–Julian Oscillation (MJO) demonstrates that eastward propagation of positive S-ab* is associated with organized deep convection. This suggests that convective activity in the tropics is a major control on variations in tropopause sharpness at intra-seasonal to interannual time-scales.

scholarly journals Characteristics of tropopause parameters as observed with GPS radio occultation

2014 ◽  
Vol 7 (5) ◽  
pp. 4693-4727 ◽  
Author(s):  
T. Rieckh ◽  
B. Scherllin-Pirscher ◽  
F. Ladstädter ◽  
U. Foelsche
Keyword(s):  
Annual Cycle ◽  
Radio Occultation ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Lapse Rate ◽  
Monthly Basis ◽  
Quasi Biennial Oscillation ◽  
Gps Radio Occultation ◽  
The Mean ◽  
Individual Profiles

Abstract. Characteristics of the lapse rate tropopause are analyzed globally for tropopause altitude and temperature using Global Positioning System (GPS) Radio Occultation (RO) data from late 2001 to 2012. RO profiles feature high vertical resolution and excellent quality in the upper troposphere and lower stratosphere, which are key factors for tropopause determination, including multiple ones. Furthermore, global coverage is reached on a monthly basis, allowing to examine both temporal and spatial characteristics thoroughly. To investigate latitudinal and longitudinal tropopause characteristics, the mean annual cycle, and inter-annual variability, we use tropopauses from individual profiles as well as their monthly mean and median for 10° zonal bands. The latitudinal structure of first tropopauses shows the well-known distribution with high (cold) tropical tropopauses and low (warm) extratropical tropopauses. In the transition zones (20° N/S to 40° N/S), individual profiles reveal varying tropopause altitudes from 7 km to 17 km due to the influence of the subtropical jets. In this region, we also find multiple tropopauses throughout the year. Longitudinal variability is strongest at northern hemispheric mid latitudes and in the Asian monsoon region. The mean annual cycle features changes in amplitude and phase depending on latitude. This is caused by different underlying physical processes (such as the Brewer-Dobson Circulation) and atmospheric dynamics (such as the very strong polar vortex in southern hemispheric winter). Inter-annual anomalies of tropopause parameters show signatures of El Niño–Southern Oscillation, the Quasi-Biennial Oscillation, and the varying strength of the polar vortex, including sudden stratospheric warming events.

COSMIC GPS Radio Occultation Temperature Profiles in Clouds

2010 ◽  
Vol 138 (4) ◽  
pp. 1104-1118 ◽  
Author(s):  
L. Lin ◽  
X. Zou ◽  
R. Anthes ◽  
Y-H. Kuo
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Radio Occultation ◽  
Lapse Rate ◽  
Gps Radio Occultation ◽  
Clear Sky ◽  
Ice Water Content ◽  
Temperature Retrieval ◽  
Sky Conditions ◽  
Ice Water

Abstract Thermodynamic states in clouds are closely related to physical processes such as phase changes of water and longwave and shortwave radiation. Global Positioning System (GPS) radio occultation (RO) data are not affected by clouds and have high vertical resolution, making them ideally suited to cloud profiling on a global basis. By comparing the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO refractivity data with those of the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and ECMWF analysis for soundings in clouds and clear air separately, a systematic bias of opposite sign was found between large-scale global analyses and the GPS RO observations under cloudy and clear-sky conditions. As a modification to the standard GPS RO wet temperature retrieval that does not distinguish between cloudy- and clear-sky conditions, a new cloudy retrieval algorithm is proposed to incorporate the knowledge that in-cloud specific humidity (which affects the GPS refractivities) should be close to saturation. To implement this new algorithm, a linear regression model for a sounding-dependent relative humidity parameter α is first developed based on a high correlation between relative humidity and ice water content. In the absence of ice water content information, α takes an empirical value of 85%. The in-cloud temperature profile is then retrieved from GPS RO data modeled by a weighted sum of refractivities with and without the assumption of saturation. Compared to the standard wet retrieval, the cloudy temperature retrieval is consistently warmer within clouds by ∼2 K and slightly colder near the cloud top (∼1 K) and cloud base (1.5 K), leading to a more rapid increase of the lapse rate with height in the upper half of the cloud, from a nearly constant moist lapse rate below and at the cloud middle (∼6°C km−1) to a value of 7.7°C km−1, which must be closer to the dry lapse rate than the standard wet retrieval.

scholarly journals A method to improve the determination of wave perturbations close to the tropopause by using a digital filter

2011 ◽  
Vol 4 (9) ◽  
pp. 1777-1784 ◽  
Author(s):  
P. Alexander ◽  
A. de la Torre ◽  
P. Llamedo ◽  
R. Hierro ◽  
T. Schmidt ◽  
...  
Keyword(s):  
Digital Filter ◽  
Radio Occultation ◽  
Atmospheric Temperature ◽  
Lapse Rate ◽  
Gps Radio Occultation ◽  
Suggested Technique ◽  
Low Latitudes ◽  
Synthetic Temperature ◽  
First Time

Abstract. GPS radio occultation satellite data allowed to analyze in the last decade for the first time a large amount of atmospheric temperature profiles including both the troposphere and the stratosphere all over the globe. Wave amplitude enhancements have been systematically observed around tropopause levels, which are apparently due to artifacts generated by any digital filter used to isolate the wave components from these data. We present a new filtering method which can be equally applied to temperature or refractivity profiles. It was tested with synthetic temperature data based on NCEP reanalyes and observed wave climatologies and it was also statistically validated with GPS radio occultation profiles from the COSMIC mission. The suggested technique significantly reduces artificial enhancements around the tropopause, mainly at low latitudes, where a sharp lapse rate change usually exists. This represents an improvement in comparison to previous applications of standard filters. In addition it would allow the study of longer vertical wavelengths than previously done with other filtering procedures.

An Analysis of the Structure and Variation of the Tropopause over China with GPS Radio Occultation Data

2011 ◽  
Vol 64 (S1) ◽  
pp. S103-S111 ◽  
Author(s):  
Xiaohua Xu ◽  
Jia Luo ◽  
Kefei Zhang
Keyword(s):  
Climate Change ◽  
Radio Occultation ◽  
Lapse Rate ◽  
Temperature Profiles ◽  
Gps Radio Occultation ◽  
Long Term Stability ◽  
The Status ◽  
High Vertical Resolution ◽  
Occultation Data ◽  
Cold Point

The status of the tropopause has impact on weather phenomena and climate change occurring in the atmosphere of the Earth. The investigation of structure and variation of the tropopause plays a significant role in an in-depth understanding of water vapour exchange, mass and chemical materials across the tropopause, and their impacts on climate change and ecological environment. With the advantages of high vertical resolution, global coverage, unbiased instrumentation, and long-term stability, GPS Radio Occultation (RO) data is ideal for the monitoring of tropopause structure. In this research, GPS RO data from the two missions, CHAMP and COSMIC, were used to assess and analyse the temporal and spatial variations in tropopause heights and temperature over China. The consistency of the precision of the GPS temperature profiles derived from the two missions were also statistically validated. The two types of tropopause, i.e. the Lapse Rate Tropopause (LRT) and the Cold Point Tropopause (CPT), were determined from the GPS RO temperature profiles, and the trend of the variations in tropopause heights and temperatures of the two types of tropopause were compared and analysed.

Optimum prediction of atmospheric temperature using GPS radio occultation measurements

2017 ◽  
Vol 919 (1) ◽  
pp. 48-51
Author(s):  
N.H. Javadov ◽  
R.A. Eminov ◽  
N.Ya. Ismailov
Keyword(s):  
Radio Occultation ◽  
General Procedure ◽  
Atmospheric Temperature ◽  
Mean Value ◽  
Optimization Criterion ◽  
Temperature Measurements ◽  
Gps Radio Occultation ◽  
Applied Optimization ◽  
Quadratic Deviation ◽  
The Mean

The matters of optimum forecasting atmospheric temperature using GPS radio occultation measurements are considered. The analysis of the available data regarding to the comparison of temperature measurements using radio occultation method and radiosondes was made. As a result it was concluded that the mean value of those results’ difference and also the mean quadratic deviation of these difference increases in common by increase of the forecasting time. In order to prevent surplus loading of telemetry channels and broadcasting inaccurate forecast values via them the optimization of general procedure of radio occultation temperature measurements are carried out using fine functions method. For optimization the concurrent parameters, changing on antiphase order are determined. It is found out that utilization of fine function method taking into account the applied optimization criterion and some limitation conditions make it possible to optimize the whole procedure of forecasting atmospheric temperature using the GPS radio occultation measurements.

scholarly journals Global 3D Features of Error Variances of GPS Radio Occultation and Radiosonde Observations

2020 ◽  
Vol 13 (1) ◽  
pp. 1
Author(s):  
Xu Xu ◽  
Xiaolei Zou
Keyword(s):  
Radio Occultation ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Error Variance ◽  
Specific Humidity ◽  
Temperature Error ◽  
Observation Error ◽  
Bending Angle ◽  
Gps Radio Occultation ◽  
Low Latitudes

Global Positioning System (GPS) radio occultation (RO) and radiosonde (RS) observations are two major types of observations assimilated in numerical weather prediction (NWP) systems. Observation error variances are required input that determines the weightings given to observations in data assimilation. This study estimates the error variances of global GPS RO refractivity and bending angle and RS temperature and humidity observations at 521 selected RS stations using the three-cornered hat method with additional ERA-Interim reanalysis and Global Forecast System forecast data available from 1 January 2016 to 31 August 2019. The global distributions, of both RO and RS observation error variances, are analyzed in terms of vertical and latitudinal variations. Error variances of RO refractivity and bending angle and RS specific humidity in the lower troposphere, such as at 850 hPa (3.5 km impact height for the bending angle), all increase with decreasing latitude. The error variances of RO refractivity and bending angle and RS specific humidity can reach about 30 N-unit2, 3 × 10−6 rad2, and 2 (g kg−1)2, respectively. There is also a good symmetry of the error variances of both RO refractivity and bending angle with respect to the equator between the Northern and Southern Hemispheres at all vertical levels. In this study, we provide the mean error variances of refractivity and bending angle in every 5°-latitude band between the equator and 60°N, as well as every interval of 10 hPa pressure or 0.2 km impact height. The RS temperature error variance distribution differs from those of refractivity, bending angle, and humidity, which, at low latitudes, are smaller (less than 1 K2) than those in the midlatitudes (more than 3 K2). In the midlatitudes, the RS temperature error variances in North America are larger than those in East Asia and Europe, which may arise from different radiosonde types among the above three regions.

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