scholarly journals Radiosonde-Observed Vertical Profiles and Increasing Trends of Temperature and Humidity during 2005–2018 at the South Pole

Atmosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 365 ◽  
Author(s):  
Min Xu ◽  
Yubin Li ◽  
Qinghua Yang ◽  
Andrew E. Gao ◽  
Bo Han ◽  
...  
Keyword(s):  
Inversion Layer ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Vertical Profiles ◽  
South Pole ◽  
The South ◽  
Yearly Average ◽  
Temperature And Humidity ◽  
Increasing Trends

The vertical profiles and trends of temperature and humidity at the South Pole up to 10 km above mean sea level (amsl) were investigated by using radiosonde data collected from March 2005 to February 2018. During an average year between 2005 and 2018, the highest (lowest) temperature in the lower troposphere was approximately −25 °C (−60 °C) in December (July) at a height of about 500 m above the surface (at the surface). A temperature inversion layer above the surface was found during the whole year but was weaker during the summer, while the inversion layers at the tropopause (about 8 km amsl) mostly disappeared during spring and winter. General warming trends were found at all heights and months, but in a few heights and months cooling trends still occurred (e.g., in September below 7 km amsl). Nevertheless, seasonal and yearly averaged temperatures all presented warming trends: 1.1, 1.3, 0.6, 1.5 and 1.1 °C/decade at the surface, and 0.7, 1.0, 0.3, 0.3 and 0.6 °C/decade for the layer average from the surface to 10 km amsl, for spring, summer, autumn, winter, and yearly average, respectively. Most of the water vapor was confined in the lowermost 3 km of the atmosphere with a maximum of 0.35 g kg−1 in December at a 200 m height above surface, and the specific humidity had the similar characteristic of annual cycle and inversion layers as the temperature. At heights below 5 km amsl, increasing trends of specific humidity larger than 0.02 g kg−1/decade occurred during summer months, including the late spring and early autumn, and the annual mean showed an increasing trend of about 0.01–0.02 g kg−1/decade. Meanwhile, above 5 km amsl, the trends became small and generally less than 0.02 g kg−1/decade in all the months, and beyond 7 km amsl the specific humidity remained almost invariant due to its small moisture content as compared with lower levels. From the surface to 10 km amsl, the specific humidity averaged trends of 0.0062, 0.019, 0.0013, 0.002 and 0.007 g kg−1/decade for spring, summer, autumn, winter and yearly average, respectively.

scholarly journals Estimation of atmospheric mixing layer height from radiosonde data

2014 ◽  
Vol 7 (6) ◽  
pp. 1701-1709 ◽  
Author(s):  
X. Y. Wang ◽  
K. C. Wang
Keyword(s):  
North America ◽  
Potential Temperature ◽  
Mixing Layer ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Consistent Estimate ◽  
Climate Data ◽  
Layer Height ◽  
Temperature And Humidity ◽  
Mixing Layer Height

Abstract. Mixing layer height (h) is an important parameter for understanding the transport process in the troposphere, air pollution, weather and climate change. Many methods have been proposed to determine h by identifying the turning point of the radiosonde profile. However, substantial differences have been observed in the existing methods (e.g. the potential temperature (θ), relative humidity (RH), specific humidity (q) and atmospheric refractivity (N) methods). These differences are associated with the inconsistency of the temperature and humidity profiles in a boundary layer that is not well mixed, the changing measurability of the specific humidity and refractivity with height, the measurement error of humidity instruments within clouds, and the general existence of clouds. This study proposes a method to integrate the information of temperature, humidity and cloud to generate a consistent estimate of h. We apply this method to high vertical resolution (~ 30 m) radiosonde data that were collected at 79 stations over North America during the period from 1998 to 2008. The data are obtained from the Stratospheric Processes and their Role in Climate Data Center (SPARC). The results show good agreement with those from N method as the information of temperature and humidity contained in N; however, cloud effects that are included in our method increased the reliability of our estimated h. From 1988 to 2008, the climatological h over North America was 1675 ± 303 m with a strong east–west gradient: higher values (generally greater than 1800 m) occurred over the Midwest US, and lower values (usually less than 1400 m) occurred over Alaska and the US West Coast.

scholarly journals Clustering a Global Field of Atmospheric Profiles by Mixture Decomposition of Copulas

2005 ◽  
Vol 22 (10) ◽  
pp. 1445-1459 ◽  
Author(s):  
Mathieu Vrac ◽  
Alain Chédin ◽  
Edwin Diday
Keyword(s):  
A Priori ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Specific Humidity ◽  
Vertical Profiles ◽  
Copula Functions ◽  
Mixture Density ◽  
Temperature And Humidity ◽  
Priori Information ◽  
Humidity Profiles

Abstract This work focuses on the clustering of a large dataset of atmospheric vertical profiles of temperature and humidity in order to model a priori information for the problem of retrieving atmospheric variables from satellite observations. Here, each profile is described by cumulative distribution functions (cdfs) of temperature and specific humidity. The method presented here is based on an extension of the mixture density problem to this kind of data. This method allows dependencies between and among temperature and moisture to be taken into account, through copula functions, which are particular distribution functions, linking a (joint) multivariate distribution with its (marginal) univariate distributions. After a presentation of vertical profiles of temperature and humidity and the method used to transform them into cdfs, the clustering method is detailed and then applied to provide a partition into seven clusters based, first, on the temperature profiles only; second, on the humidity profiles only; and, third, on both the temperature and humidity profiles. The clusters are statistically described and explained in terms of airmass types, with reference to meteorological maps. To test the robustness and the relevance of the method for a larger number of clusters, a partition into 18 classes is established, where it is shown that even the smallest clusters are significant. Finally, comparisons with more classical efficient clustering or model-based methods are presented, and the advantages of the approach are discussed.

scholarly journals A New Technique for Estimation of Lower-Tropospheric Temperature and Water Vapor Profiles from Radio Occultation Refractivity

2009 ◽  
Vol 26 (6) ◽  
pp. 1075-1089 ◽  
Author(s):  
D. Jagadheesha ◽  
B. Simon ◽  
P-K. Pal ◽  
P. C. Joshi ◽  
A. Maheshwari
Keyword(s):  
Radio Occultation ◽  
Specific Humidity ◽  
New Technique ◽  
Radiosonde Data ◽  
Boreal Summer ◽  
Tropospheric Temperature ◽  
Lower Altitude ◽  
Temperature And Humidity ◽  
The Tropics ◽  
Humidity Profiles

Abstract An empirical technique is proposed to obtain temperature and humidity profiles over the tropics using radio occultation refractivity profiles and surface/available lower-altitude temperature and pressure measurements over humid tropical regions. The technique is tested on a large number of diverse radiosonde-derived refractivity profiles over the tropics (30°S–30°N) and selected Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation refractivity profiles that have collocated radiosonde observations over the region 10°S–30°N during the boreal summer of 2006. In a number of cases, the results were in good agreement with the collocated radiosonde data. The error statistics of temperature and humidity profiles obtained from the proposed technique are discussed and compared with the previously published results from another technique and also with the results of a one-dimensional variational data assimilation (1DVAR) technique given with COSMIC data. It is found that the previously published results and proposed technique are marginally better (worse) in reproducing observed relative humidity (specific humidity) when compared to the 1DVAR technique. The proposed new technique is applied on COSMIC refractivity profiles over the Bay of Bengal during summer 2007 to derive changes in vertical thermal and moisture changes in the troposphere between active and break phases of the monsoon pattern and many of the observed features are captured reasonably well.

scholarly journals The Intraseasonal and Interannual Variability of Arctic Temperature and Specific Humidity Inversions

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 214 ◽  
Author(s):  
Lejiang Yu ◽  
Qinghua Yang ◽  
Mingyu Zhou ◽  
Xubin Zeng ◽  
Donald H. Lenschow ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Intraseasonal Variability ◽  
Intraseasonal Oscillation ◽  
Lower Troposphere ◽  
Specific Humidity ◽  
The Arctic ◽  
Self Organizing Map ◽  
Eastern Hemisphere ◽  
Temperature And Humidity ◽  
Arctic Temperature

Temperature and humidity inversions are common in the Arctic’s lower troposphere, and are a crucial component of the Arctic’s climate system. In this study, we quantify the intraseasonal oscillation of Arctic temperature and specific humidity inversions and investigate its interannual variability using data from the Surface Heat Balance of the Arctic (SHEBA) experiment from October 1997 to September 1998 and the European Centre for Medium-Range Forecasts (ECMWF) Reanalysis (ERA)-interim for the 1979–2017 period. In January 1998, there were two noticeable elevated inversions and one surface inversion. The transitions between elevated and surface-based inversions were associated with the intraseasonal variability of the temperature and humidity differences between 850 and 950 hPa. The self-organizing map (SOM) technique is utilized to obtain the main modes of surface and elevated temperature and humidity inversions on intraseasonal time scales. Low (high) pressure and more (less) cloud cover are related to elevated (surface) temperature and humidity inversions. The frequency of strong (weak) elevated inversions over the eastern hemisphere has decreased (increased) in the past three decades. The wintertime Arctic Oscillation (AO) and Arctic Dipole (AD) during their positive phases have a significant effect on the occurrence of surface and elevated inversions for two Nodes only.

Parameterization of clear sky effective emissivity under surface-based temperature inversion at Dome C and South Pole, Antarctica

2013 ◽  
Vol 25 (5) ◽  
pp. 697-710 ◽  
Author(s):  
Maurizio Busetto ◽  
Christian Lanconelli ◽  
Mauro Mazzola ◽  
Angelo Lupi ◽  
Boyan Petkov ◽  
...  
Keyword(s):  
Inversion Layer ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Ground Level ◽  
Temperature Inversion ◽  
Maximum Temperature ◽  
South Pole ◽  
Effective Emissivity ◽  
Clear Sky ◽  
Good Proxy

AbstractFor most parts of the year the Antarctic Plateau has a surface temperature inversion with strength c. 20 K. Under such conditions the warmer air at the top of the inversion layer contributes more to the clear sky atmospheric longwave radiation at surface level than does the colder air near the ground. Hence, it is more appropriate to relate longwave irradiance (LWI) to the top of the inversion layer temperature (Tm) than to the ground level temperature (Tg). Analysis of radio soundings carried out at Dome C and South Pole during 2006–08 shows that the temperature at 400 m above the surface (T400) is a good proxy for Tm and is linearly related to Tg with correlation coefficients greater than 0.8. During summer, radiosonde measurements show almost isothermal conditions, hence T400 still remains a good proxy for the lower troposphere maximum temperature. A methodology is presented to parameterize the clear sky effective emissivity in terms of the troposphere maximum temperature, using ground temperature measurements. The predicted LWI values for both sites are comparable with those obtained using radiative transfer models, while for Dome C the bias of 0.8 W m-2 and the root mean square (RMS) of 6.2 W m-2 are lower than those calculated with previously published parametric equations.

scholarly journals Estimation of temperature and humidity from MST radar observations

2001 ◽  
Vol 19 (8) ◽  
pp. 855-861 ◽  
Author(s):  
K. Mohan ◽  
D. Narayana Rao ◽  
T. Narayana Rao ◽  
S. Raghavan
Keyword(s):  
Refractive Index ◽  
Dissipation Rate ◽  
Radiosonde Data ◽  
Refractive Index Gradient ◽  
Measured Temperature ◽  
Vertical Profiles ◽  
Radar Observations ◽  
Mst Radar ◽  
Temperature And Humidity ◽  
Index Gradient

Abstract. Retrieval of vertical profiles of temperature and humidity parameters using a VHF radar is described in this paper. For this, Indian MST radar located at Gadanki (13.5° N, 79.2° E) has been operated in a special mode. First, vertical velocities are collected continuously using the radar and are subjected to Fast Fourier Transform (FFT) analysis to obtain Brunt-Väisälä oscillations. From the measured Brunt-Väisälä  oscillations, temperature profile is obtained from the radar observations following Revathy et al. (1996). The various terms required for the retrieval of vertical profiles of humidity are the eddy dissipation rate, ε, the volume reflectivity, η, and the potential refractive index gradient, M. The eddy dissipation rate, ε, is calculated from the spectral width after removing the effects due to non-turbulence. The volume reflectivity, η, of the turbulence scattering is calculated using the signal-to-noise ratio as a function of height. The potential refractive index gradient, M, is evaluated using the measured Brunt-Väisälä  oscillations, the eddy dissipation rate and the volume reflectivity, η. Vertical profiles of humidity are retrieved following Tsuda (1997) using the radar derived temperature as well as the balloon measured temperature and are compared with the humidity as measured by the radiosonde. The sign of the potential refractive index gradient, M, is taken from the simultaneous measurements of balloon soundings. The retrieved vertical profiles of temperature and humidity have been compared with the radiosonde data, which are released simultaneously with the radar observations at the radar site. A fairly good comparison is seen between the two measurements on some days and there are some discrepancies on some other days. The strengths and limitations in estimating the vertical profiles of temperature and humidity from the radar observations are discussed.Key words. Atmospheric composition and structure (pressure, density and temperature; enhancements and techniques)

scholarly journals A Look at the Surface-Based Temperature Inversion on the Antarctic Plateau

2005 ◽  
Vol 18 (11) ◽  
pp. 1673-1696 ◽  
Author(s):  
Stephen R. Hudson ◽  
Richard E. Brandt
Keyword(s):  
Temperature Inversion ◽  
Temperature Data ◽  
Radiosonde Data ◽  
Lower Latitude ◽  
South Pole ◽  
The South ◽  
Antarctic Plateau ◽  
Air Temperatures ◽  
The Antarctic ◽  
Longwave Flux

Abstract Data from radiosondes, towers, and a thermistor string are used to characterize the temperature inversion at two stations: the Amundsen-Scott Station at the South Pole, and the somewhat higher and colder Dome C Station at a lower latitude. Ten years of temperature data from a 22-m tower at the South Pole are analyzed. The data include 2- and 22-m temperatures for the entire period and 13-m temperatures for the last 2 yr. Statistics of the individual temperatures and the differences among the three levels are presented for summer (December and January) and winter (April–September). The relationships of temperature and inversion strength in the lowest 22 m with wind speed and downward longwave flux are examined for the winter months. Two preferred regimes, one warming and one cooling, are found in the temperature versus longwave flux data, but the physical causes of these regimes have not been determined. The minimum temperatures and the maximum inversions tend to occur not with calm winds, but with winds of 3–5 m s−1, likely due to the inversion wind. This inversion wind also explains why the near-surface winds at South Pole blow almost exclusively from the northeast quadrant. Temperature data from the surface to 2 m above the surface from South Pole in the winter of 2001 are presented, showing that the steepest temperature gradient in the entire atmosphere is in the lowest 20 cm. The median difference between the temperatures at 2 m and the surface is over 1.0 K in winter; under clear skies this difference increases to about 1.3 K. Monthly mean temperature profiles of the lowest 30 km of the atmosphere over South Pole are presented, based on 10 yr of radiosonde data. These profiles show large variations in lower-stratospheric temperatures, and in the strength and depth of the surface-based inversion. The near-destruction of a strong inversion at South Pole during 7 h on 8 September 1992 is examined using a thermal-conductivity model of the snowpack, driven by the measured downward longwave flux. The downward flux increased when a cloud moved over the station, and it seems that this increase in radiation alone can explain the magnitude and timing of the warming near the surface. Temperature data from the 2003/04 and 2004/05 summers at Dome C Station are presented to show the effects of the diurnal cycle of solar elevation over the Antarctic Plateau. These data include surface temperature and 2- and 30-m air temperatures, as well as radiosonde air temperatures. They show that strong inversions, averaging 10 K between the surface and 30 m, develop quickly at night when the sun is low in the sky, but are destroyed during the middle of the day. The diurnal temperature range at the surface was 13 K, but only 3 K at 30 m.

scholarly journals Vertical profile observations of water vapor deuterium excess in the lower troposphere

2019 ◽  
Vol 19 (17) ◽  
pp. 11525-11543 ◽  
Author(s):  
Olivia E. Salmon ◽  
Lisa R. Welp ◽  
Michael E. Baldwin ◽  
Kristian D. Hajny ◽  
Brian H. Stirm ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Inversion Layer ◽  
Lower Troposphere ◽  
Phase Changes ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Deuterium Excess ◽  
Airborne Measurements

Abstract. We use airborne measurements of water vapor (H2Ov) stable isotopologues and complementary meteorological observations to examine how boundary layer (BL) dynamics, cloud processing, and atmospheric mixing influence the vertical structure of δD, δ18O, and deuterium excess (d excess =δD–8×δ18O) in the BL, inversion layer (INV), and lower free troposphere (FT). Flights were conducted around two continental US cities in February–March 2016 and included vertical profiles extending from near the surface to ≤2 km. We examine observations from three unique case study flights in detail. One case study shows observations that are consistent with Rayleigh isotopic distillation theory coinciding with clear skies, dry adiabatic lapse rates within the boundary layer, and relatively constant vertical profiles of wind speed and wind direction. This suggests that the air mass retained the isotopic fingerprint of dehydration during moist adiabatic processes upwind of the study area. Also, observed d-excess values in the free troposphere were sometimes larger than Rayleigh theory predicts, which may indicate mixing of extremely dehydrated air from higher altitudes. The two remaining case studies show isotopic anomalies in the d-excess signature relative to Rayleigh theory and indicate cloud processes and complex boundary layer development. The most notable case study with stratocumulus clouds present had extremely low (negative) d-excess values at the interface of the inversion layer and the free troposphere, which is possibly indicative of cloud or rain droplet evaporation. We discuss how in situ H2Ov stable isotope measurements, and d excess in particular, could be useful for improving our understanding of water phase changes, transport, and mixing that occurs between the BL, INV, and FT.

scholarly journals Estimation of atmospheric mixing layer height from radiosonde data

2014 ◽  
Vol 7 (2) ◽  
pp. 1247-1273
Author(s):  
X. Y. Wang ◽  
K. C. Wang
Keyword(s):  
North America ◽  
Potential Temperature ◽  
Mixing Layer ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Consistent Estimate ◽  
Climate Data ◽  
Layer Height ◽  
Temperature And Humidity ◽  
Mixing Layer Height

Abstract. Mixing layer height (h) is an important parameter for understanding the transport process in the troposphere, air pollution, weather and climate change. Many methods have been proposed to determine h by identifying the turning point of the radiosonde profile. However, substantial differences have been observed in the existing methods (e.g., the potential temperature (θ), relative humidity (RH), specific humidity (q) and atmospheric refractivity (N) methods). These differences are associated with the inconsistency of the temperature and humidity profiles in a boundary layer that is not well mixed, the changing measurability of the specific humidity and refractivity with height, the measurement error of humidity instruments within clouds, and the general existence of clouds. This study proposes a method to integrate the information of temperature, humidity and cloud to generate a consistent estimate of h. We apply this method to high vertical resolution (~ 30 m) radiosonde data that were collected at 79 stations over North America during the period from 1998 to 2008; the data are obtained from the Stratospheric Processes and their Role in Climate Data Center (SPARC). The results show good agreement with those from N method as the information of temperature and humidity contained in N; however cloud effects that are included in our method increased the reliability of h. Furthermore, our results agree well with the independent h that was determined from lidar observations. From 1988 to 2008, the climatological h over North America was 1675± 303 m with a strong east–west gradient: higher values (generally greater than 1800 m) occurred over the Midwest US, and lower values (usually less than 1400 m) occurred over Alaska and the US west coast.

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