Using Radio Occultation to Detect Clouds in the Middle and Upper Troposphere

2021 ◽  
Author(s):  
Jeana Mascio ◽  
Stephen S. Leroy ◽  
Robert P. d’Entremont ◽  
Thomas Connor ◽  
E. Robert Kursinski
Keyword(s):  
Relative Humidity ◽  
High Performance ◽  
Radio Occultation ◽  
Three Dimensional ◽  
Roc Curves ◽  
Lapse Rate ◽  
Cloud Detection ◽  
Upper Troposphere ◽  
Temperature Lapse Rate ◽  
Direct Sensitivity

AbstractRadio occultation (RO) measurements have little direct sensitivity to clouds, but recent studies have shown that they may have an indirect sensitivity to thin, high clouds that are difficult to detect using conventional passive space-based cloud sensors. We implement two RO-based cloud detection (ROCD) algorithms for atmospheric layers in the middle and upper troposphere. The first algorithm is based on the methodology of a previous study, which explored signatures caused by upper tropospheric clouds in RO profiles according to retrieved relative humidity, temperature lapse rate, and gradients in log-refractivity (ROCD-P), and the second is based on inferred relative humidity alone (ROCD-M). In both, atmospheric layers are independently predicted as cloudy or clear based on observational data, including high performance RO retrievals. In a demonstration, we use data from 10 days spanning seven months in 2020 of FORMOSAT-7/COSMIC-2. We use the forecasts of NOAA GFS to aid in the retrieval of relative humidity. The prediction is validated with a cloud truth dataset created from the imagery of the GOES-16 Advanced Baseline Imager (ABI) satellite and the GFS three-dimensional analysis of cloud state conditions. Given these two algorithms for the presence or absence of clouds, confusion matrices and receiver operating characteristic (ROC) curves are used to analyze how well these algorithms perform. The ROCD-M algorithm has a balanced accuracy, which defines the quality of the classification test that considers both the sensitivity and specificity, greater than 70% for all altitudes between 6 and 10.25 km.

scholarly journals CAPE Variations in the Current Climate and in a Climate Change

1998 ◽  
Vol 11 (8) ◽  
pp. 1997-2015 ◽  
Author(s):  
Bing Ye ◽  
Anthony D. Del Genio ◽  
Kenneth K-W. Lo
Keyword(s):  
Climate Change ◽  
Relative Humidity ◽  
General Circulation ◽  
Large Scale ◽  
Tropical Pacific ◽  
Lapse Rate ◽  
Moist Convection ◽  
Upper Troposphere ◽  
Current Climate ◽  
The Tropical Pacific

Abstract Observed variations of convective available potential energy (CAPE) in the current climate provide one useful test of the performance of cumulus parameterizations used in general circulation models (GCMs). It is found that frequency distributions of tropical Pacific CAPE, as well as the dependence of CAPE on surface wet-bulb potential temperature (Θw) simulated by the Goddard Institute for Space Studies’s GCM, agree well with that observed during the Australian Monsoon Experiment period. CAPE variability in the current climate greatly overestimates climatic changes in basinwide CAPE in the tropical Pacific in response to a 2°C increase in sea surface temperature (SST) in the GCM because of the different physics involved. In the current climate, CAPE variations in space and time are dominated by regional changes in boundary layer temperature and moisture, which in turn are controlled by SST patterns and large-scale motions. Geographical thermodynamic structure variations in the middle and upper troposphere are smaller because of the canceling effects of adiabatic cooling and subsidence warming in the rising and sinking branches of the Walker and Hadley circulations. In a forced equilibrium global climate change, temperature change is fairly well constrained by the change in the moist adiabatic lapse rate and thus the upper troposphere warms to a greater extent than the surface. For this reason, climate change in CAPE is better predicted by assuming that relative humidity remains constant and that the temperature changes according to the moist adiabatic lapse rate change of a parcel with 80% relative humidity lifted from the surface. The moist adiabatic assumption is not symmetrically applicable to a warmer and colder climate: In a warmer regime moist convection determines the tropical temperature structure, but when the climate becomes colder the effect of moist convection diminishes and the large-scale dynamics and radiative processes become relatively important. Although a prediction based on the change in moist adiabat matches the GCM simulation of climate change averaged over the tropical Pacific basin, it does not match the simulation regionally because small changes in the general circulation change the local boundary layer relative humidity by 1%–2%. Thus, the prediction of regional climate change in CAPE is also dependent on subtle changes in the dynamics.

scholarly journals O CLIMA E SUA INFLUÊNCIA NA DISTRIBUIÇÃO DA FLORESTA OMBRÓFILA DENSA NA SERRA DA PRATA, MORRETES, PARANÁ

FLORESTA ◽  
2011 ◽  
Vol 41 (3) ◽  
Author(s):  
Christopher Thomas Blum ◽  
Carlos Vellozo Roderjan ◽  
Franklin Galvão
Keyword(s):  
Relative Humidity ◽  
Meteorological Data ◽  
Lapse Rate ◽  
Mountain Range ◽  
Air Masses ◽  
Temperature Lapse Rate ◽  
Serra Do Mar ◽  
Average Temperature ◽  
Climatic Transition ◽  
Apparent Influence

O estudo teve como objetivo caracterizar aspectos climáticos, com enfoque na temperatura e umidade relativa do ar e sua influência sobre a distribuição da vegetação numa encosta da Serra da Prata, Morretes, Paraná, coberta pelas formações Submontana e Montana da Floresta Ombrófila Densa. Entre julho de 2009 e junho de 2010 foram obtidos dados meteorológicos, aos 400 e 1.000 m s.n.m. As temperaturas médias no período foram 19,0 ºC (400 m) e 16,3 ºC (1.000 m). A taxa de redução térmica com a elevação altitudinal foi 0,44 ºC/100 m. Detectou-se uma região de transição climática em torno dos 700 m de altitude, com o clima Cfb acima e o Cfa abaixo. A isoterma da temperatura média de 13 ºC no mês mais frio, estimada para a região dos 800 m s.n.m., coincide com o limite inferior de ocorrência da formação Montana, denotando a influência das baixas temperaturas na diferenciação da vegetação. As médias de umidade relativa do ar foram elevadas, devido ao constante aporte das massas de ar úmido oriundas do oceano. As médias das amplitudes diárias de temperatura e umidade foram muito semelhantes para as duas altitudes, demonstrando que a variação altitudinal parece não exercer influência sobre suas variações diárias na encosta estudada.Palavras-chave:  Gradiente altitudinal; Serra do Mar; Floresta Atlântica; temperatura; umidade relativa do ar. AbstractClimate and his influence over the Atlantic Dense Rainforest distribution in the Prata Mountain Range, Morretes, Paraná, South Brazil. This study aimed to characterize climatic aspects, focusing air temperature and relative humidity, as well as its influence to vegetation distribution in a slope of Prata Mountain Range, Morretes, Paraná, covered by Submontane and Montane formations of the Atlantic Rainforest. Between July of 2009 and June of 2010 meteorological data was collected, at 400 and 1,000 m a.s.l. The average temperature along this period was 19.0 ºC (400 m) and 16.3 ºC (1,000 m). The temperature lapse rate was 0.44 ºC/100 m. It was detected a climatic transition region at about 700 m a.s.l., with the Cfb type above, and the Cfa type below. The isotherm of the average temperature of 13 ºC in the coldest month, estimated for the region of about 800 m a.s.l., agrees with the inferior limit of the Montane formation, denoting influence of low temperatures in the vegetation distinction. The air relative humidity average was high, because the regular arrival of moist air masses from the ocean. The average of daily amplitude of temperature and relative humidity were very similar for both studied altitudes, denoting not apparent influence of the altitudinal variation to the daily variation of these climatic variables in the slope.Keywords:              Altitudinal gradient; Serra do Mar; Atlantic Ombrophilous Dense Forest; temperature; air relative humidity.

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 Impact of gravity waves on the motion and distribution of atmospheric ice particles

2018 ◽  
Vol 18 (14) ◽  
pp. 10799-10823 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals' presence. The wave-driven localization is consistent with temperature–cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

scholarly journals Effect of the relative humidity on an industrial plume behavior

2013 ◽  
Vol 8 (3) ◽  
pp. 297-305
Keyword(s):  
Relative Humidity ◽  
Meteorological Data ◽  
Source Parameters ◽  
Momentum Equation ◽  
Lapse Rate ◽  
Maximum Height ◽  
Atmospheric Conditions ◽  
Empirical Formulas ◽  
Ratio Distribution ◽  
Temperature Lapse Rate

In order to accurately predict the pollutant concentrations and the plume trajectory in the atmosphere, it is necessary to take into account the effects of interactions between the plume and the surrounding environment. In fact, the atmospheric conditions have a lot of influence on the plume behavior. Earlier models were based on statistical approach. However, this approach presents many shortcomings, in that way they are unable to take directly into account some atmospheric properties such as the moisture of the air. A complete model is the one that solves the entire set of momentum equation completed by energy and species equations. A number of approximate predictive methods for the plume flow in stratified surroundings have been developed in the literature such as Abraham (1965), Schwartz and Tulin (1972), Sneck and Brown (1974), Wright (1984) and Hwang and Chiang (1986). In this work, we use the lagrangian concept based on the so-called projected area entrainment in its latest formulation (Lee and Cheung 1990) to predict the effect of relative humidity on the plume behavior. Input-required data include source parameters such as the gas exhaust conditions (temperature release, exit velocity, mixing ratios), physical dimensions (diameter and height of stack) and meteorological data. In the present work, only idealized meteorological conditions which neglect the vertical variation of the wind speed, the temperature lapse rate and the relative humidity are considered. The output of the model gives an idea on characteristics parameters of the plume such as its trajectory, its temperature and mixing ratio distribution and its length of visibility. The model validation is accomplished through a comparison of the computed plume maximum height with results obtained using empirical formulas (Hanna, 1972). Also, the calculated plume visibility length is confronted to the ADMS results obtained by Carruthers et al. (2000). The effect of relative humidity is then investigated.

scholarly journals Determination of Best Tropopause Definition for Convective Transport Studies

2018 ◽  
Vol 75 (10) ◽  
pp. 3433-3446 ◽  
Author(s):  
Emily M. Maddox ◽  
Gretchen L. Mullendore
Keyword(s):  
Mass Transport ◽  
Potential Vorticity ◽  
Deep Convection ◽  
Three Dimensional ◽  
Static Stability ◽  
Convective Transport ◽  
Lapse Rate ◽  
Tracer Concentration ◽  
Temperature Lapse Rate ◽  
Cloud Resolving Model

An idealized three-dimensional cloud-resolving model is used to investigate the sensitivity of cross-tropopause convective mass transport to tropopause definition. A simulation is conducted to encompass the growth and decay cycle of a supercell thunderstorm, with a focus on irreversible transport above the tropopause. Five previously published tropopause definitions are evaluated: World Meteorological Organization (WMO) temperature lapse rate, potential vorticity, static stability, vertical curvature of the Brunt–Väisälä frequency, and stratospheric tracer concentration. By analyzing the behavior of different definitions both during and after active convection, we are able to define “best” choices for tropopause definitions as those that return to states most closely matching the preconvective environment. Potential vorticity and stratospheric tracer concentration are shown to perform poorly when analyzing deep convection. The WMO thermal tropopause and static stability definitions are found to perform the best, providing similar tropopause placement and quantities of irreversible mass transport. This investigation highlights the challenges of defining a tropopause in the vicinity of deep convection and demonstrates the need to clearly communicate calculation methods and threshold choices in the literature.

scholarly journals KARAKTERISTIK KETINGGIAN DASAR AWAN YANG DIUKUR DENGAN SENSOR INFRA MERAH RADIOMETER PADA PUNCAK MUSIM HUJAN DI JABODETABEK.

2020 ◽  
Vol 20 (1) ◽  
pp. 39-45
Author(s):  
Findy Renggono
Keyword(s):  
Lapse Rate ◽  
Cloud Base ◽  
Base Temperature ◽  
Cloud Detection ◽  
Weather Modification ◽  
Temperature Lapse Rate ◽  
Cloud Properties ◽  
Comparison Results ◽  
Rain Radar ◽  
Cloud Base Height

IntisariInformasi mengenai tinggi dasar awan penting bagi penelitian atmosfer dan juga sebagai masukan bagi pemodelan cuaca. Pada kegiatan modifikasi cuaca, informasi ini juga sangat penting dalam menentukan awan yang akan disemai. Dalam tulisan ini, pengukuran tinggi dasar awan dilakukan dengan menggunakan sensor infra merah yang terpasang pada radiometer. Sensor infra merah ini akan mengukur suhu dasar awan yang kemudian dapat diketahui ketinggiannya dengan melihat temperatur lapse rate. Hasil pengukuran dibandingkan dengan hasil pengamatan awan oleh micro rain radar yang terletak di lokasi yang sama. Hasil pengukuran dari kedua peralatan ini menunjukkan kesesuaian antara kemunculan awan pada micro rain radar yang ditunjukkan dengan struktur vertikal awan dengan hasil pengamatan dengan IRT dari radiometer. Pengamatan selama puncak musim hujan di Jabodetabek (Januari – Maret 2019) menunjukan adanya pola harian yang cukup jelas. AbstractInformation on cloud properties is important for atmospheric research and as well as for weather modeling. In weather modification, this information is very important for cloud seeding strategy. The observation of cloud base height is carried out using infrared sensors mounted on a radiometer. These infrared thermometer sensors are capable of detecting the cloud base temperature, the cloud base height is obtained by looking at the temperature lapse rate retrieved from radiometer observation. The results were compared with the cloud observation by micro rain radar which is located at the same location. The comparison results of these two instruments show that the consistency of cloud detection was good. Based on the observation during the peak of the rainy season in Jabodetabek (January-March 2019), it is shown a fairly clear daily pattern

A Diagnostic Equation for Tendency of Lapse-Rate-Tropopause Heights and Its Application

2019 ◽  
Vol 76 (11) ◽  
pp. 3337-3350
Author(s):  
Masashi Kohma ◽  
Kaoru Sato
Keyword(s):  
Radio Occultation ◽  
Potential Temperature ◽  
Vertical Gradient ◽  
Reanalysis Data ◽  
Lapse Rate ◽  
Synoptic Scale ◽  
Temperature Lapse Rate ◽  
Planetary Scale ◽  
Baroclinic Waves ◽  
Occultation Data

Abstract The tropopause is the boundary between the troposphere and stratosphere and is normally defined by the temperature lapse rate. Previous studies have noted that synoptic-scale and planetary-scale disturbances bring about lapse-rate-tropopause (LRT) height fluctuations on time scales from several days to several years. In the present study, a diagnostic expression for the tendency of LRT height is derived by assuming that the LRT can be characterized as a discontinuity in the vertical gradient of the potential temperature. In addition, the contribution from each term in the thermodynamic equation to the LRT height is quantified. The derived equation is validated by examining the time variation of the LRT height associated with baroclinic waves in an idealized numerical calculation, that of the zonal-mean LRT height in GPS radio occultation data, and that of the LRT height in reanalysis data.

scholarly journals Impact of gravity waves on the motion and distribution of atmospheric ice particles

2017 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, a special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals presence. The wave-driven localization is consistent with temperature-cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

An Analytical Model for Tropical Relative Humidity

2014 ◽  
Vol 27 (19) ◽  
pp. 7432-7449 ◽  
Author(s):  
David M. Romps
Keyword(s):  
Relative Humidity ◽  
Analytical Model ◽  
Climate Models ◽  
Global Climate ◽  
Invariant Function ◽  
Global Climate Models ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Cloud Resolving Model ◽  
Simple Ratio

Abstract An analytical model is derived for tropical relative humidity using only the Clausius–Clapeyron relation, hydrostatic balance, and a bulk-plume water budget. This theory is constructed for radiative–convective equilibrium and compared against a cloud-resolving model. With some reinterpretation of variables, it can be applied more generally to the entire tropics. Given four variables—pressure, temperature, and the fractional entrainment and detrainment rates—the equations predict the relative humidity (RH) and the temperature lapse rate analytically. The RH is a simple ratio involving the fractional detrainment rate and the water-vapor lapse rate. When integrated upward in height, the equations give profiles of RH and temperature for a convecting atmosphere. The theory explains the magnitude of RH and the “C” shape of the tropospheric RH profile. It also predicts that RH is an invariant function of temperature as the atmosphere warms, and this behavior matches what has been seen in global climate models and what is demonstrated here with cloud-resolving simulations. Extending the theory to include the evaporation of hydrometeors, a lower bound is derived for the precipitation efficiency (PE) at each height: PE > 1 − RH. In a cloud-resolving simulation, this constraint is obeyed with the PE profile taking the shape of an inverted C shape.

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