scholarly journals Regional Apparent Boundary Layer Lapse Rates Determined from CALIPSO and MODIS Data for Cloud-Height Determination

2014 ◽  
Vol 53 (4) ◽  
pp. 990-1011 ◽  
Author(s):  
Sunny Sun-Mack ◽  
Patrick Minnis ◽  
Yan Chen ◽  
Seiji Kato ◽  
Yuhong Yi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Thermal Structure ◽  
Lower Troposphere ◽  
Free Water ◽  
Lapse Rate ◽  
Monthly Means ◽  
Spatial Error ◽  
Modis Data ◽  
Low Cloud ◽  
Lapse Rates

AbstractReliably determining low-cloud heights using a cloud-top temperature from satellite infrared imagery is often challenging because of difficulties in characterizing the local thermal structure of the lower troposphere with the necessary precision and accuracy. To improve low-cloud-top height estimates over water surfaces, various methods have employed lapse rates anchored to the sea surface temperature to replace the boundary layer temperature profiles that relate temperature to altitude. To further improve low-cloud-top height retrievals, collocated Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data taken from July 2006 to June 2007 and from June 2009 to May 2010 (2 yr) for single-layer low clouds are used here with numerical weather model analyses to develop regional mean boundary apparent lapse rates. These parameters are designated as apparent lapse rates because they are defined using the cloud-top temperatures from satellite retrievals and surface skin temperatures; they do not represent true lapse rates. Separate day and night, seasonal mean lapse rates are determined for 10′-resolution snow-free land, water, and coastal regions, while zonally dependent lapse rates are developed for snow/ice-covered areas for use in the Clouds and the Earth’s Radiant Energy System (CERES) Edition 4 cloud property retrieval system (CCPRS-4). The derived apparent lapse rates over ice-free water range from 5 to 9 K km−1 with mean values of about 6.9 and 7.2 K km−1 during the day and night, respectively. Over land, the regional values vary from 3 to 8 K km−1, with day and night means of 5.5 and 6.2 K km−1, respectively. The zonal-mean apparent lapse rates over snow and ice surfaces generally decrease with increasing latitude, ranging from 4 to 8 K km−1. All of the CCPRS-4 lapse rates were used along with five other lapse rate techniques to retrieve cloud-top heights for 2 months of independent Aqua MODIS data. When compared with coincident CALIPSO data for October 2007, the mean cloud-top height differences between CCPRS-4 and CALIPSO during the daytime (nighttime) are 0.04 ± 0.61 km (0.10 ± 0.62 km) over ice-free water, −0.06 ± 0.85 km (−0.01 ± 0.83 km) over snow-free land, and 0.38 ± 0.95 km (0.03 ± 0.92 km) over snow-covered areas. The CCPRS-4 regional monthly means are generally unbiased and lack spatial error gradients seen in the comparisons for most of the other techniques. Over snow-free land, the regional monthly-mean errors range from −0.28 ± 0.74 km during daytime to 0.04 ± 0.78 km at night. The water regional monthly means are, on average, 0.04 ± 0.44 km less than the CALIPSO values during day and night. Greater errors are realized for snow-covered regions. Overall, the CCPRS-4 lapse rates yield the smallest RMS differences for all times of day over all areas both for individual retrievals and monthly means. These new regional apparent lapse rates, used in processing CERES Edition 4 data, should provide more accurate low-cloud-type heights than previously possible using satellite imager data.

On the Relationship between Stratiform Low Cloud Cover and Lower-Tropospheric Stability

2006 ◽  
Vol 19 (24) ◽  
pp. 6425-6432 ◽  
Author(s):  
Robert Wood ◽  
Christopher S. Bretherton
Keyword(s):  
Boundary Layer ◽  
Temperature Profile ◽  
Cloud Cover ◽  
Cloud Amount ◽  
Lapse Rate ◽  
Stratus Cloud ◽  
Low Clouds ◽  
Wide Range ◽  
Low Cloud ◽  
Low Cloud Cover

Abstract Observations in subtropical regions show that stratiform low cloud cover is well correlated with the lower-troposphere stability (LTS), defined as the difference in potential temperature θ between the 700-hPa level and the surface. The LTS can be regarded as a measure of the strength of the inversion that caps the planetary boundary layer (PBL). A stronger inversion is more effective at trapping moisture within the marine boundary layer (MBL), permitting greater cloud cover. This paper presents a new formulation, called the estimated inversion strength (EIS), to estimate the strength of the PBL inversion given the temperatures at 700 hPa and at the surface. The EIS accounts for the general observation that the free-tropospheric temperature profile is often close to a moist adiabat and its lapse rate is strongly temperature dependent. Therefore, for a given LTS, the EIS is greater at colder temperatures. It is demonstrated that while the seasonal cycles of LTS and low cloud cover fraction (CF) are strongly correlated in many regions, no single relationship between LTS and CF can be found that encompasses the wide range of temperatures occurring in the Tropics, subtropics, and midlatitudes. However, a single linear relationship between CF and EIS explains 83% of the regional/seasonal variance in stratus cloud amount, suggesting that EIS is a more regime-independent predictor of stratus cloud amount than is LTS under a wide range of climatological conditions. The result has some potentially important implications for how low clouds might behave in a changed climate. In contrast to Miller’s thermostat hypothesis that a reduction in the lapse rate (Clausius–Clapeyron) will lead to increased LTS and increased tropical low cloud cover in a warmer climate, the results here suggest that low clouds may be much less sensitive to changes in the temperature profile if the vertical profile of tropospheric warming follows a moist adiabat.

A Review of Planetary Boundary Layer Parameterization Schemes and Their Sensitivity in Simulating Southeastern U.S. Cold Season Severe Weather Environments

2015 ◽  
Vol 30 (3) ◽  
pp. 591-612 ◽  
Author(s):  
Ariel E. Cohen ◽  
Steven M. Cavallo ◽  
Michael C. Coniglio ◽  
Harold E. Brooks
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Turbulent Mixing ◽  
Convective Available Potential Energy ◽  
Lower Troposphere ◽  
Cold Season ◽  
Severe Weather ◽  
Parameterization Schemes ◽  
Lapse Rates ◽  
Local Schemes

Abstract The representation of turbulent mixing within the lower troposphere is needed to accurately portray the vertical thermodynamic and kinematic profiles of the atmosphere in mesoscale model forecasts. For mesoscale models, turbulence is mostly a subgrid-scale process, but its presence in the planetary boundary layer (PBL) can directly modulate a simulation’s depiction of mass fields relevant for forecast problems. The primary goal of this work is to review the various parameterization schemes that the Weather Research and Forecasting Model employs in its depiction of turbulent mixing (PBL schemes) in general, and is followed by an application to a severe weather environment. Each scheme represents mixing on a local and/or nonlocal basis. Local schemes only consider immediately adjacent vertical levels in the model, whereas nonlocal schemes can consider a deeper layer covering multiple levels in representing the effects of vertical mixing through the PBL. As an application, a pair of cold season severe weather events that occurred in the southeastern United States are examined. Such cases highlight the ambiguities of classically defined PBL schemes in a cold season severe weather environment, though characteristics of the PBL schemes are apparent in this case. Low-level lapse rates and storm-relative helicity are typically steeper and slightly smaller for nonlocal than local schemes, respectively. Nonlocal mixing is necessary to more accurately forecast the lower-tropospheric lapse rates within the warm sector of these events. While all schemes yield overestimations of mixed-layer convective available potential energy (MLCAPE), nonlocal schemes more strongly overestimate MLCAPE than do local schemes.

Deriving Marine-Boundary-Layer Lapse Rate from Collocated CALIPSO, MODIS, and AMSR-E Data to Study Global Low-Cloud Height Statistics

2008 ◽  
Vol 5 (4) ◽  
pp. 649-652 ◽  
Author(s):  
Dong Wu ◽  
Yongxiang Hu ◽  
M. Patrick McCormick ◽  
Kuan-Man Xu ◽  
Zhaoyan Liu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Lapse Rate ◽  
Cloud Height ◽  
Low Cloud

Lapse rate deviations from the moist adiabat in the tropical upper troposphere in climate models

2020 ◽  
Author(s):  
Paul Keil ◽  
Hauke Schmidt ◽  
Bjorn Stevens
Keyword(s):  
Climate Models ◽  
Lower Troposphere ◽  
Lapse Rate ◽  
Cmip5 Models ◽  
Upper Troposphere ◽  
Microphysical Parameters ◽  
The Mean ◽  
Lapse Rates ◽  
The Tropics ◽  
Mean State

<p>The tropospheric lapse rate in the tropics follows a moist adiabat quite closely and is mainly set by surface temperature and humidity in the convecting regions. Therefore, warming or biases at the surface are transferred via the moist adiabat to the upper troposphere. However, climate models show large discrepancies in the upper troposphere and recent observed upper tropospheric warming is around 0.5K weaker than predicted by the moist adiabat theory. Here we use the control simulations of the CMIP5 ensemble to show that large differences in the upper troposphere exist in the mean state that are unrelated to inter-model differences in the lower troposphere. In fact, CMIP5 models diverge (positively and negatively) from the moist pseudoadiabat by up to 2K at 300hPa. Precipitation weighted SSTs have recently been used to resolve the discrepancy between models and observations in upper tropospheric warming, but we show that they are not able to explain the differences in the mean state. While it is difficult to exactly depict the reasons for the inter-model spread, we demonstrate how the upper tropospheric lapse rate can deviate from the moist adiabat for the same lower tropospheric state with AMIP experiments. For this we use the ICON-A model, in which we tune convective and microphysical parameters. An improved understanding of the effect of different parameterisations on the models' lapse rates may help to better understand differences in the response to global warming.</p>

Stratocumulus Cloud-Top Height Estimates and Their Climatic Implications

2009 ◽  
Vol 22 (17) ◽  
pp. 4652-4666 ◽  
Author(s):  
Paquita Zuidema ◽  
David Painemal ◽  
Simon de Szoeke ◽  
Chris Fairall
Keyword(s):  
Boundary Layer ◽  
Lapse Rate ◽  
Cloud Base ◽  
Imaging Spectrometer ◽  
Boundary Layer Height ◽  
Coastal Jet ◽  
Southeast Pacific ◽  
Low Cloud ◽  
Daily Sampling ◽  
Moderate Resolution

Abstract A depth-dependent boundary layer lapse rate was empirically deduced from 156 radiosondes released during six month-long research cruises to the southeast Pacific sampling a variety of stratocumulus conditions. The lapse-rate dependence on boundary layer height is weak, decreasing from a best fit of 7.6 to 7.2 K km−1 as the boundary layer deepens from 800 m to 2 km. Ship-based cloud-base heights up to 800 m correspond well to lifting condensation levels, indicating well-mixed conditions, with cloud bases >800 m often 200–600 m higher than the lifting condensation levels. The lapse rates were combined with Moderate Resolution Imaging Spectrometer 11-μm-derived cloud-top temperatures and satellite microwave-derived sea surface temperatures to estimate stratocumulus cloud-top heights. The October-mean cloud-top height structure of the southeast Pacific was then spatially and diurnally characterized. Coastal shoaling is apparent, but so is a significant along-coast cloud-top height gradient, with a pronounced elevation of the cloud-top heights above the Arica Bight at ∼20°S. Diurnal cloud-top height variations (inferred from irregular 4-times-daily sampling) can locally reach 250 m in amplitude, and they can help to visualize offshore propagation of free-tropospheric vertical motions. A shallow boundary layer associated with the Chilean coastal jet expands to its north and west in the afternoon. Cloud-top heights above the Arica Bight region are depressed in the afternoon, which may mean that increased subsidence from sensible heating of the Andes dominates an afternoon increase in convergence/upward motion at the exit of the Chilean coastal jet. In the southeast Atlantic during October, the stratocumulus cloud-top heights are typically lower than those in the southeast Pacific. A coastal jet region can also be identified through its low cloud-top heights. Coastal shoaling of the South Atlantic stratocumulus region is mostly uniform with latitude, in keeping with the more linear Namibian/Angolan coastline. The southeast Atlantic shallow cloudy boundary layer extends farther offshore than in the southeast Pacific, particularly at 15°S.

scholarly journals Low clouds suppress Arctic air formation and amplify high-latitude continental winter warming

2015 ◽  
Vol 112 (37) ◽  
pp. 11490-11495 ◽  
Author(s):  
Timothy W. Cronin ◽  
Eli Tziperman
Keyword(s):  
Air Temperature ◽  
High Latitude ◽  
Climate Model ◽  
Lower Troposphere ◽  
Surface Air Temperature ◽  
Cloud Feedback ◽  
Lapse Rate ◽  
Initial State ◽  
Low Clouds ◽  
Low Cloud

High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable climates. We use an idealized single-column atmospheric model across a range of conditions to study the polar night process of air mass transformation from high-latitude maritime air, with a prescribed initial temperature profile, to much colder high-latitude continental air. We find that a low-cloud feedback—consisting of a robust increase in the duration of optically thick liquid clouds with warming of the initial state—slows radiative cooling of the surface and amplifies continental warming. This low-cloud feedback increases the continental surface air temperature by roughly two degrees for each degree increase of the initial maritime surface air temperature, effectively suppressing Arctic air formation. The time it takes for the surface air temperature to drop below freezing increases nonlinearly to ∼10 d for initial maritime surface air temperatures of 20 °C. These results, supplemented by an analysis of Coupled Model Intercomparison Project phase 5 climate model runs that shows large increases in cloud water path and surface cloud longwave forcing in warmer climates, suggest that the “lapse rate feedback” in simulations of anthropogenic climate change may be related to the influence of low clouds on the stratification of the lower troposphere. The results also indicate that optically thick stratus cloud decks could help to maintain frost-free winter continental interiors in equable climates.

scholarly journals Climatological studies of lapse rates during summer months vis-à-vis All India Summer Monsoon Rainfall

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 95-110
Author(s):  
U. R. JOSHI ◽  
G. S. PRAKASA RAO ◽  
SHRAVAN KUMAR
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Lower Troposphere ◽  
Summer Monsoon Rainfall ◽  
Lapse Rate ◽  
Upper Troposphere ◽  
India Summer Monsoon ◽  
India Summer Monsoon Rainfall ◽  
The Mean ◽  
Lapse Rates

The combined mean normal lapse rates for 0000 and 1200 UTC for 35 Radiosonde (RS) stations based on the period 1971-99 during the summer months (March to May) were worked out for standard levels and analysed.  To know whether any relationship exists between the distribution of summer lapse rates and the all India summer monsoon rainfall (June to September),  the mean lapse rates for three good monsoon years and six deficient years during the same period were worked out separately and the Lapse Rate Anomalies (LRAs) were examined in detail.  In excessive monsoon rainfall years the LRAs were generally negative (instable atmosphere) during summer months (March-May) in the lower and middle troposphere and the anomalies were positive in the upper troposphere.  In the deficient monsoon years, the case is reverse i.e., LRAs were positive in the lower troposphere (inhibiting the convective activity) while they were negative in the middle and upper troposphere.  The same results were noticed in the recent worst monsoon year 2002 and bad monsoon year 2004.   The LRAs thus give signals in the months of March to May regarding the ensuing monsoon rainfall qualitatively and can be used as one of the tools for long range forecasting.

The Stratification of the Atmosphere1 (I)

1950 ◽  
Vol 31 (3) ◽  
pp. 71-78 ◽  
Author(s):  
H. Flohn ◽  
R. Penndorf
Keyword(s):  
Thermal Structure ◽  
Mixing Layer ◽  
Sudden Change ◽  
Atomic Layer ◽  
Bottom Layer ◽  
Lapse Rate ◽  
New Classification ◽  
Isothermal Layer ◽  
Outer Atmosphere ◽  
Definition Of

A suitable nomenclature for atmospheric strata as well as a clear definition of the boundaries is proposed. The necessity of such a new classification is stressed. The atmosphere is divided into an inner and an outer atmosphere; from the latter particles may escape. The inner atmosphere is divided into three spheres—troposphere, stratosphere, and ionosphere—with each sphere in turn being subdivided into 3 or 4 layers. The new classification is based upon the thermal structure of the atmosphere.' Boundaries of each layer are fixed by a sudden change of lapse rate. The bottom layer, the ground layer, the advection layer, and the tropopause layer are subdivisions of the troposphere. The advantages gained by defining a separate tropopause layer as part of the troposphere are discussed in detail. Its upper boundary is assumed to be situated at 12 km over temperate latitudes. The stratosphere, consisting of an isothermal layer, a warm layer, and an upper mixing layer, extends from 12 to 80 km. The atmosphere between 80 and 800 km is occupied by the ionosphere, the subdivisions of which are the E-layer, the Flayer and the atomic layer. Above that height the exosphere exists.

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 Evaluation of the AMPS Boundary Layer Simulations on the Ross Ice Shelf, Antarctica, with Unmanned Aircraft Observations

2017 ◽  
Vol 56 (8) ◽  
pp. 2239-2258 ◽  
Author(s):  
Jonathan D. Wille ◽  
David H. Bromwich ◽  
John J. Cassano ◽  
Melissa A. Nigro ◽  
Marian E. Mateling ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Relative Humidity ◽  
High Wind ◽  
Ice Shelf ◽  
High Wind Speed ◽  
Near Surface ◽  
Ross Ice Shelf ◽  
Low Cloud ◽  
The Antarctic

AbstractAccurately predicting moisture and stability in the Antarctic planetary boundary layer (PBL) is essential for low-cloud forecasts, especially when Antarctic forecasters often use relative humidity as a proxy for cloud cover. These forecasters typically rely on the Antarctic Mesoscale Prediction System (AMPS) Polar Weather Research and Forecasting (Polar WRF) Model for high-resolution forecasts. To complement the PBL observations from the 30-m Alexander Tall Tower! (ATT) on the Ross Ice Shelf as discussed in a recent paper by Wille and coworkers, a field campaign was conducted at the ATT site from 13 to 26 January 2014 using Small Unmanned Meteorological Observer (SUMO) aerial systems to collect PBL data. The 3-km-resolution AMPS forecast output is combined with the global European Centre for Medium-Range Weather Forecasts interim reanalysis (ERAI), SUMO flights, and ATT data to describe atmospheric conditions on the Ross Ice Shelf. The SUMO comparison showed that AMPS had an average 2–3 m s−1 high wind speed bias from the near surface to 600 m, which led to excessive mechanical mixing and reduced stability in the PBL. As discussed in previous Polar WRF studies, the Mellor–Yamada–Janjić PBL scheme is likely responsible for the high wind speed bias. The SUMO comparison also showed a near-surface 10–15-percentage-point dry relative humidity bias in AMPS that increased to a 25–30-percentage-point deficit from 200 to 400 m above the surface. A large dry bias at these critical heights for aircraft operations implies poor AMPS low-cloud forecasts. The ERAI showed that the katabatic flow from the Transantarctic Mountains is unrealistically dry in AMPS.

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