scholarly journals Comparison between Backscatter Lidar and Radiosonde Measurements of the Diurnal and Nocturnal Stratification in the Lower Troposphere

2007 ◽  
Vol 24 (7) ◽  
pp. 1231-1244 ◽  
Author(s):  
Giovanni Martucci ◽  
Renaud Matthey ◽  
Valentin Mitev ◽  
Hans Richner
Keyword(s):  
Mixed Layer Depth ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Correlation Coefficients ◽  
Residual Layer ◽  
Radiosonde Data ◽  
Aerosol Layer ◽  
Temperature Profiles ◽  
Layer Depth ◽  
Stable Conditions

Abstract A collection of boundary layer heights has been derived from measurements performed by a ground-based backscatter lidar in Neuchâtel, Switzerland (47.000°N, 6.967°E, 485 m ASL). A dataset of 98 cases have been collected during 2 yr. From these data, 61 are noon and 37 are midnight cases. The following two different schemes were used to retrieve the mixed layer depth and the height of the residual layer from the measurements: the gradient and variance methods. The obtained values were compared with those derived from the potential temperature profiles as computed from radiosonde data. For nocturnal cases, the height of the first aerosol layer above the residual layer was also compared to the corresponding potential temperature value. Correlation coefficients between lidar and radiosonde in both convective and stable conditions are between 0.88 and 0.97.

The Convolution of Dynamics and Moisture with the Presence of Shortwave Absorbing Aerosols over the Southeast Atlantic

2015 ◽  
Vol 28 (5) ◽  
pp. 1997-2024 ◽  
Author(s):  
Adeyemi A. Adebiyi ◽  
Paquita Zuidema ◽  
Steven J. Abel
Keyword(s):  
Lower Troposphere ◽  
Radiosonde Data ◽  
Aerosol Layer ◽  
Low Level ◽  
Moisture Effects ◽  
Fine Mode ◽  
Absorbing Aerosols ◽  
St Helena ◽  
Offshore Transport ◽  
Continental Outflow

Abstract Biomass burning aerosols seasonally overlie the subtropical southeast Atlantic stratocumulus deck. Previous modeling and observational studies have postulated a semidirect effect whereby shortwave absorption by the aerosol warms and stabilizes the lower troposphere, thickening the low-level clouds. The focus herein is on the dynamical and moisture effects that may be convoluted with the semidirect effect. Almost-daily radiosonde data from remote St. Helena Island (15.9°S, 5.6°W), covering September–October 2000–11, are combined with daily spatial averages (encompassing the island) of the MODIS clear-sky fine-mode aerosol optical depth (). Increases in are associated with increases in 750–500-hPa moisture content. The net maximum longwave cooling by moisture of almost 0.45 K day−1 reduces the aerosol layer warming from shortwave absorption. ERA-Interim spatial composites show that polluted conditions are associated with a strengthening of a deep land-based anticyclone over southern Africa, facilitating the westward offshore transport of both smoke and moisture at 600 hPa. The shallower surface-based South Atlantic anticyclone exhibits a less pronounced shift to the northeast, strengthening the low-level coastal jet exiting into the stratocumulus deck and cooling 1000-hPa potential temperatures. Warm continental outflow further increases the 800-hPa potential temperatures (), reinforcing the lower tropospheric stability () over the stratocumulus deck. Enhanced southerly dry air advection also strengthens the cloud-top humidity inversion. The increased stability helps explain an observed decrease in cloud-top heights despite an anomalous reduction in subsidence. The changes to the horizontal dynamics enhance low-level cloudiness. These are separate but not necessarily distinct from an aerosol semidirect effect, encouraging care in attribution studies.

Climatology of mixed layer depth in the Gulf of Aden derived from in situ temperature profiles

2019 ◽  
Vol 75 (4) ◽  
pp. 335-347 ◽  
Author(s):  
Cheriyeri P. Abdulla ◽  
Mohammed A. Alsaafani ◽  
Turki M. Alraddadi ◽  
Alaa M. Albarakati
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Temperature Profiles ◽  
Gulf Of Aden ◽  
Layer Depth

scholarly journals GPS radio occultation with CHAMP and SAC-C: global monitoring of thermal tropopause parameters

2005 ◽  
Vol 5 (6) ◽  
pp. 1473-1488 ◽  
Author(s):  
T. Schmidt ◽  
S. Heise ◽  
J. Wickert ◽  
G. Beyerle ◽  
C. Reigber
Keyword(s):  
Standard Deviation ◽  
Potential Temperature ◽  
Weather Forecast ◽  
Lapse Rate ◽  
Radiosonde Data ◽  
Temperature Profiles ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Medium Range Weather Forecast ◽  
Satellite Missions

Abstract. In this study the global lapse-rate tropopause (LRT) pressure, temperature, potential temperature, and sharpness are discussed based on Global Positioning System (GPS) radio occultations (RO) from the German CHAMP (CHAllenging Minisatellite Payload) and the U.S.-Argentinian SAC-C (Satelite de Aplicaciones Cientificas-C) satellite missions. Results with respect to seasonal variations are compared with operational radiosonde data and ECMWF (European Centre for Medium-Range Weather Forecast) operational analyses. Results on the tropical quasi-biennial oscillation (QBO) are updated from an earlier study. CHAMP RO data are available continuously since May 2001 with on average 150 high resolution temperature profiles per day. SAC-C data are available for several periods in 2001 and 2002. In this study temperature data from CHAMP for the period May 2001-December 2004 and SAC-C data from August 2001-October 2001 and March 2002-November 2002 were used, respectively. The bias between GPS RO temperature profiles and radiosonde data was found to be less than 1.5K between 300 and 10hPa with a standard deviation of 2-3K. Between 200-20hPa the bias is even less than 0.5K (2K standard deviation). The mean deviations based on 167699 comparisons between CHAMP/SAC-C and ECMWF LRT parameters are (-2.1±37.1)hPa for pressure and (0.1±4.2)K for temperature. Comparisons of LRT pressure and temperature between CHAMP and nearby radiosondes (13230) resulted in (5.8±19.8)hPa and (-0.1±3.3)K, respectively. The comparisons between CHAMP/SAC-C and ECMWF show on average the largest differences in the vicinity of the jet streams with up to 700m in LRT altitude and 3K in LRT temperature, respectively. The CHAMP mission generates the first long-term RO data set. Other satellite missions will follow (GRACE, COSMIC, MetOp, TerraSAR-X, EQUARS) generating together some thousand temperature profiles daily.

scholarly journals Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

2011 ◽  
Vol 8 (3) ◽  
pp. 1505-1533
Author(s):  
K. Castro-Morales ◽  
J. Kaiser
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Potential Temperature ◽  
World Ocean ◽  
Reference Value ◽  
Relative Difference ◽  
Layer Depth ◽  
Biological Production ◽  
World Ocean Atlas

Abstract. Concentrations of oxygen (O2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes; for example, in the context of net and gross biological production estimates. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using O2 may be different to zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by numerical analysis of O2 profiles in coastal areas of the Southern Ocean and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e. zmix(Δθ = 0.2 °C) and zmix(Δθ = 0.5 °C), and potential density differences, i.e. zmix(Δσθ = 0.03 kg m−3) and zmix(Δσθ = 0.125 kg m−3), showed that zmix(O2) closely follows zmix(Δσθ = 0.03 kg m−3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(Δσθ = 0.03 kg m−3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

scholarly journals Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

Ocean Science ◽  
2012 ◽  
Vol 8 (1) ◽  
pp. 1-10 ◽  
Author(s):  
K. Castro-Morales ◽  
J. Kaiser
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Potential Temperature ◽  
World Ocean ◽  
Reference Value ◽  
Relative Difference ◽  
Layer Depth ◽  
Bellingshausen Sea ◽  
World Ocean Atlas ◽  
Mixed Layers

Abstract. Concentrations of oxygen (O2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using oxygen may be different than zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e., zmix(0.2 °C) and zmix(0.5 °C), and potential density differences, i.e., zmix(0.03 kg m−3) and zmix(0.125 kg m−3), showed that zmix(O2) closely follows zmix(0.03 kg m−3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(0.03 kg m−3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

scholarly journals Planetary Boundary Layer variability over New Delhi, India, during EUCAARI project

2018 ◽  
Author(s):  
Konstantina Nakoudi ◽  
Elina Giannakaki ◽  
Aggeliki Dandou ◽  
Maria Tombrou ◽  
Mika Komppula
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Feature Detection ◽  
Potential Temperature ◽  
Satellite Observations ◽  
Radiosonde Data ◽  
New Delhi ◽  
Aerosol Layer ◽  
Lidar Measurements ◽  
Good Agreement

Abstract. Ground-based lidar measurements were performed at Gual Pahari measurement station, approximately 20 km South of New Delhi, India, from March 2008 to March 2009. The height of the Planetary Boundary Layer (PBL) was retrieved with a portable Raman lidar system, utilizing the modified Wavelet Covariance Transform (WCT) method. The lidar derived PBL heights were compared to radiosonde data, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite observations and two atmospheric models. The results were also analyzed on a seasonal basis. To examine the difficulties of PBL lidar detection under different meteorological and aerosol load conditions we focused on three case studies of PBL diurnal evolution. In the presence of a multiple aerosol layer structure, the WCT method exhibited high efficiency in PBL height determination. Good agreement with the European Center for Medium-range Weather Forecasts (ECMWF) and the Weather Research and Forecasting (WRF) estimations was found (r=0.69 and r=0.74, respectively) for a cumulus convection case. In the aforementioned cases, temperature, relative humidity and potential temperature radiosonde profiles were well compared to the respective WRF profiles. The Bulk Richardson Number scheme, which was applied to radiosonde profile data, was in good agreement with lidar data, especially during daytime (r=0.68). The overall comparison with CALIPSO satellite observations; namely, CALIOP Level 2 Aerosol Layer Product, was very satisfying (r=0.84), with CALIPSO Feature Detection Algorithms slightly overestimating PBL height. Lidar measurements revealed that the maximum PBL height was reached approximately three hours after the solar noon, whilst the daily evolution of the PBL was completed, on average, one hour earlier. The PBL diurnal cycle was also analyzed using ECMWF estimations, which produced a stronger cycle during the winter and pre-monsoon period. The seasonal analysis of lidar PBL heights yielded a less pronounced PBL cycle than the one expected from long term climate records. The lowest mean daytime PBL height (695 m) appeared in winter, while the highest mean daytime PBL height (1326 m) was found in the monsoon season as expected. PBL daily growth rates exhibited also a weak seasonal variability.

Interannual variability of the Tropical Indian Ocean mixed layer depth

2012 ◽  
Vol 40 (3-4) ◽  
pp. 743-759 ◽  
Author(s):  
M. G. Keerthi ◽  
M. Lengaigne ◽  
J. Vialard ◽  
C. de Boyer Montégut ◽  
P. M. Muraleedharan
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Ocean Mixed Layer Depth

scholarly journals Summertime increases in upper-ocean stratification and mixed-layer depth

Nature ◽  
2021 ◽  
Vol 591 (7851) ◽  
pp. 592-598
Author(s):  
Jean-Baptiste Sallée ◽  
Violaine Pellichero ◽  
Camille Akhoudas ◽  
Etienne Pauthenet ◽  
Lucie Vignes ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Upper Ocean ◽  
Layer Depth ◽  
Ocean Stratification
Sign in / Sign up

Export Citation Format

Share Document