scholarly journals Comparison and Calculation of Different Atmospheric Delay Models Using Atmospheric Parameters of VLBI Stations of China

1993 ◽  
Vol 156 ◽  
pp. 212-212
Author(s):  
Zhigen Yang
Keyword(s):  
Elevation Angle ◽  
Mapping Function ◽  
Physical Models ◽  
Lapse Rate ◽  
Tropospheric Temperature ◽  
Atmospheric Parameters ◽  
Temperature Lapse Rate ◽  
Atmospheric Delay ◽  
Vlbi Observations ◽  
The Difference

The values of the atmospheric time delay for the “Chao”, “Marini” and “CfA−2.2” mapping function are calculated by using the atmospheric parameters in summer and winter at Shanghai, Kunming and Urumqi station respectively. A comparison among these values shows that the derivations of “Marini” from “Chao” and “CfA” are relatively large. On the other hand, the difference of values between the “Chao” and the “CfA” in the case of ∊ = 40° ∼ 10°, which is the average for the three stations, is from +1 mm to +47 mm for the “wet” part of the delay in summer, while is from −2 mm to −28 mm for the “dry” part in winter. For the case of low elevation angle ɛ ≐ 5°, the difference for the “wet” part can be about 400 mm in summer. Therefore, it is indispensable to make a further comparison between “Chao” and “CfA” mapping function by using the data of VLBI observations, in order to make a better revision to the adopted models of atmospheric delay.The monthly averages of the height of tropopause ht and the tropospheric temperature lapse rate βt for the three stations mentioned above are used to calculate the dry atmospheric delay by the “CfA” mapping function. The results show that the amplitudes of the annual changing of delay dτa, which is caused by ht and βt for the case of ∊ = 20° ∼ 10° at Urumqi station, are about 1 ∼ 5 mm and 2 ∼ 15 mm respectively. Therefore, taking the parameters of ht and βt of the stations into account in “CfA” model, instead of using fixed constants, would be much favourable for the requirements of 1 ps precision of VLBI physical models.

scholarly journals Long-Term Observations of Microwave Brightness Temperatures over a Metropolitan Area: Comparison of Radiometric Data and Spectra Simulated with the Use of Radiosonde Measurements

2021 ◽  
Vol 13 (11) ◽  
pp. 2061
Author(s):  
Mikhail V. Belikovich ◽  
Mikhail Yu. Kulikov ◽  
Dmitry S. Makarov ◽  
Natalya K. Skalyga ◽  
Vitaly G. Ryskin ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Elevation Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Systematic Bias ◽  
Tropospheric Temperature ◽  
Absorption Model ◽  
60 Ghz ◽  
Error Budget ◽  
The Difference

Ground-based microwave radiometers are increasingly used in operational meteorology and nowcasting. These instruments continuously measure the spectra of downwelling atmospheric radiation in the range 20–60 GHz used for the retrieval of tropospheric temperature and water vapor profiles. Spectroscopic uncertainty is an important part of the retrieval error budget, as it leads to systematic bias. In this study, we analyze the difference between observed and simulated microwave spectra obtained from more than four years of microwave and radiosonde observations over Nizhny Novgorod (56.2° N, 44° E). We focus on zenith-measured and elevation-scanning data in clear-sky conditions. The simulated spectra are calculated by a radiative transfer model with the use of radiosonde profiles and different absorption models, corresponding to the latest spectroscopy research. In the case of zenith-measurements, we found a systematic bias (up to ~2 K) of simulated spectra at 51–54 GHz. The sign of bias depends on the absorption model. A thorough investigation of the error budget points to a spectroscopic nature of the observed differences. The dependence of the results on the elevation angle and absorption model can be explained by the basic properties of radiative transfer and by cloud contamination at elevation angles.

scholarly journals Modeling Seasonal Changes in the Temperature Lapse Rate in a Northern Thailand Mountainous Area

2010 ◽  
Vol 49 (6) ◽  
pp. 1233-1246 ◽  
Author(s):  
Hikaru Komatsu ◽  
Hirofumi Hashimoto ◽  
Tomonori Kume ◽  
Nobuaki Tanaka ◽  
Natsuko Yoshifuji ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Temperature Data ◽  
Base Stations ◽  
Lapse Rate ◽  
Mountain Forest ◽  
Chiang Mai ◽  
Northern Thailand ◽  
Temperature Lapse Rate ◽  
Regional Circulation ◽  
The Difference

Abstract Temperature data in the mountain forest regions are often extrapolated from temperature data recorded at base stations at lower elevation. Such extrapolation is often based on elevation differences between target regions and base stations at low elevation assuming a constant temperature lapse rate throughout the year. However, this assumption might be problematic where slope circulation is active and decoupled from the regional circulation. To model the seasonal change in the lapse rate, the authors compared daily maximum (Tmax) and minimum temperatures (Tmin) observed at a mountain forest site (Kog–Ma; 1300-m altitude) with those observed at the bottom of the basin (Chiang–Mai; 314-m altitude) in northern Thailand, where slope circulation is active and decoupled from the regional circulation. The difference in Tmax between Kog–Ma and Chiang–Mai (ΔTmax; Kog–Ma minus Chiang–Mai) was relatively unchanged throughout the year. However, the difference in Tmin between Kog–Ma and Chiang–Mai (ΔTmin) changed seasonally. Thus, assuming a constant lapse rate throughout the year could cause large errors in extrapolating Tmin data in mountainous areas in northern Thailand. The difference ΔTmin was related to nighttime net radiation (Rn), suggesting that nocturnal drainage flow affects the determination of ΔTmin. This relationship would be useful in formulating seasonal changes in the lapse rate for Tmin. As Rn data are generally unavailable for meteorological stations, an index that relates to the lapse rate for Tmin and is calculated from Tmax and Tmin data is proposed. This index might be useful for accurately estimating Tmin values in mountainous regions in northern Thailand.

scholarly journals Sensitivity of the Intensity and Structure of Tropical Cyclones to Tropospheric Stability Conditions

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 411
Author(s):  
Tetsuya Takemi ◽  
Shota Yamasaki
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Tropical Cyclones ◽  
Static Stability ◽  
Sea Surface ◽  
Lapse Rate ◽  
Tropospheric Temperature ◽  
Tropopause Height ◽  
Temperature Lapse Rate ◽  
Warm Core

The intensity of tropical cyclones (TCs) is controlled by their environmental conditions. In addition to the sea surface temperature, tropospheric temperature lapse rate and tropopause height are highly variable. This study investigates the sensitivity of the intensity and structure of TCs to environmental static stability with a fixed sea surface temperature by conducting a large ensemble of axisymmetric numerical experiments in which tropopause height and tropospheric temperature lapse rate are systematically changed based on the observed environmental properties for TCs that occurred in the western North Pacific. The results indicate that the intensity of the simulated TCs changes more sharply with the increase in the temperature lapse rate than with the increase in the tropopause height. The increases in the intensity of TCs are 1.3–1.9 m s−1 per 1% change of the lapse rate and 0.1–0.5 m s−1 per 1% change of the tropopause height. With the increase in the intensity of TCs, supergradient wind at low levels and double warm core structures are evident. Specifically, the formation of the warm core at the lower levels is closely tied with the intensification of TCs, and the temperature excess of the lower warm core becomes larger in higher lapse rate cases.

scholarly journals Thermal structure of intense convective clouds derived from GPS radio occultations

2012 ◽  
Vol 12 (12) ◽  
pp. 5309-5318 ◽  
Author(s):  
R. Biondi ◽  
W. J. Randel ◽  
S.-P. Ho ◽  
T. Neubert ◽  
S. Syndergaard
Keyword(s):  
Thermal Structure ◽  
Deep Convection ◽  
Lapse Rate ◽  
Orthogonal Polarization ◽  
Cold Temperatures ◽  
Temperature Lapse Rate ◽  
Convective Systems ◽  
Convective Clouds ◽  
Strong Inversion ◽  
Cloud Tops

Abstract. Thermal structure associated with deep convective clouds is investigated using Global Positioning System (GPS) radio occultation measurements. GPS data are insensitive to the presence of clouds, and provide high vertical resolution and high accuracy measurements to identify associated temperature behavior. Deep convective systems are identified using International Satellite Cloud Climatology Project (ISCCP) satellite data, and cloud tops are accurately measured using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIPSO) lidar observations; we focus on 53 cases of near-coincident GPS occultations with CALIPSO profiles over deep convection. Results show a sharp spike in GPS bending angle highly correlated to the top of the clouds, corresponding to anomalously cold temperatures within the clouds. Above the clouds the temperatures return to background conditions, and there is a strong inversion at cloud top. For cloud tops below 14 km, the temperature lapse rate within the cloud often approaches a moist adiabat, consistent with rapid undiluted ascent within the convective systems.

scholarly journals Climate Drift in the CMIP5 Models*

2013 ◽  
Vol 26 (21) ◽  
pp. 8597-8615 ◽  
Author(s):  
Alexander Sen Gupta ◽  
Nicolas C. Jourdain ◽  
Jaclyn N. Brown ◽  
Didier Monselesan
Keyword(s):  
Climate Models ◽  
Coupled Model ◽  
Deep Ocean ◽  
Internal Variability ◽  
Correction Method ◽  
Physical Models ◽  
Cmip5 Models ◽  
Steric Sea Level ◽  
Biogeochemical Models ◽  
The Difference

Abstract Climate models often exhibit spurious long-term changes independent of either internal variability or changes to external forcing. Such changes, referred to as model “drift,” may distort the estimate of forced change in transient climate simulations. The importance of drift is examined in comparison to historical trends over recent decades in the Coupled Model Intercomparison Project (CMIP). Comparison based on a selection of metrics suggests a significant overall reduction in the magnitude of drift from phase 3 of CMIP (CMIP3) to phase 5 of CMIP (CMIP5). The direction of both ocean and atmospheric drift is systematically biased in some models introducing statistically significant drift in globally averaged metrics. Nevertheless, for most models globally averaged drift remains weak compared to the associated forced trends and is often smaller than the difference between trends derived from different ensemble members or the error introduced by the aliasing of natural variability. An exception to this is metrics that include the deep ocean (e.g., steric sea level) where drift can dominate in forced simulations. In such circumstances drift must be corrected for using information from concurrent control experiments. Many CMIP5 models now include ocean biogeochemistry. Like physical models, biogeochemical models generally undergo long spinup integrations to minimize drift. Nevertheless, based on a limited subset of models, it is found that drift is an important consideration and must be accounted for. For properties or regions where drift is important, the drift correction method must be carefully considered. The use of a drift estimate based on the full control time series is recommended to minimize the contamination of the drift estimate by internal variability.

scholarly journals A Two-Stage Quality Control Method for 2-m Temperature Observations Using Biweight Means and a Progressive EOF Analysis

2013 ◽  
Vol 141 (2) ◽  
pp. 798-808 ◽  
Author(s):  
Zhifang Xu ◽  
Yi Wang ◽  
Guangzhou Fan
Keyword(s):  
Quality Control ◽  
Control Method ◽  
Control Process ◽  
Lapse Rate ◽  
Systematic Bias ◽  
Eof Analysis ◽  
Two Stage ◽  
Quality Control Method ◽  
Quality Control Process ◽  
The Difference

Abstract The relatively smooth terrain embedded in the numerical model creates an elevation difference against the actual terrain, which in turn makes the quality control of 2-m temperature difficult when forecast or analysis fields are utilized in the process. In this paper, a two-stage quality control method is proposed to address the quality control of 2-m temperature, using biweight means and a progressive EOF analysis. The study is made to improve the quality control of the observed 2-m temperature collected by China and its neighboring areas, based on the 6-h T639 analysis from December 2009 to February 2010. Results show that the proposed two-stage quality control method can secure the needed quality control better, compared with a regular EOF quality control process. The new method is, in particular, able to remove the data that are dotted with consecutive errors but showing small fluctuations. Meanwhile, compared with the lapse rate of temperature method, the biweight mean method is able to remove the systematic bias generated by the model. It turns out that such methods make the distributions of observation increments (the difference between observation and background) more Gaussian-like, which ensures the data quality after the quality control.

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