Cloud-top pressure retrieval with DSCOVR EPIC oxygen A- and B-band observations

Abstract. An analytic transfer inverse model for Earth Polychromatic Imaging Camera (EPIC) observations is proposed to retrieve the cloud-top pressure (CTP) with the consideration of in-cloud photon penetration. In this model, an analytic equation was developed to represent the reflection at the top of the atmosphere from above cloud, in cloud, and below cloud. The coefficients of this analytic equation can be derived from a series of EPIC simulations under different atmospheric conditions using a nonlinear regression algorithm. With estimated cloud pressure thickness, the CTP can be retrieved from EPIC observation data by solving the analytic equation. To simulate the EPIC measurements, a program package using the double-k approach was developed. Compared to line-by-line calculation, this approach can calculate high-accuracy results with a 100-fold computation time reduction. During the retrieval processes, two kinds of retrieval results, i.e., baseline CTP and retrieved CTP, are provided. The baseline CTP is derived without considering in-cloud photon penetration, and the retrieved CTP is derived by solving the analytic equation, taking into consideration in-cloud and below-cloud interactions. The retrieved CTPs for the oxygen A and B bands are smaller than their related baseline CTP. At the same time, both baseline CTP and retrieved CTP at the oxygen B band are larger than those at the oxygen A band. Compared to the difference in baseline CTP between the B band and A band, the difference in retrieved CTP between these two bands is generally reduced. Out of around 10 000 cases, in retrieved CTP between the A and B bands we found an average bias of 93 mb with a standard deviation of 81 mb. The cloud layer top pressure from Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements is used for validation. Under single-layer cloud situations, the retrieved CTPs for the oxygen A band agree well with the CTPs from CALIPSO, the mean difference of which within 5 mb in the case study. Under multiple-layer cloud situations, the CTPs derived from EPIC measurements may be larger than the CTPs of high-level thin clouds due to the effect of photon penetration.

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Cloud top pressure retrieval with DSCOVR-EPIC oxygen A and B bands observation

10.5194/amt-2019-373 ◽

2020 ◽

Author(s):

Bangsheng Yin ◽

Qilong Min ◽

Emily Morgan ◽

Yuekui Yang ◽

Alexander Marshak ◽

...

Keyword(s):

Linear Regression ◽

High Accuracy ◽

Transfer Model ◽

Observation Data ◽

Atmospheric Conditions ◽

Analytic Equation ◽

Retrieval Processes ◽

Imaging Camera ◽

The Difference ◽

Cloud Top Pressure

Abstract. An analytic transfer model for Earth Polychromatic Imaging Camera (EPIC) observation was proposed to retrieve the cloud top pressure (CTP) with considering in-cloud photon penetration. In this model, an analytic equation was developed to represent the reflection at top of atmosphere (TOA) from above cloud, in-cloud and below-cloud. The coefficients of this analytic equation can be derived from a series of EPIC simulations under different atmospheric conditions using a non-linear regression algorithm. With estimated cloud pressure thickness, the CTP can be retrieved from EPIC observation data by solving the analytic equation. To simulate the EPIC measurements, a program package using the double-k approach was developed, which can calculate high-accuracy results with a one-hundred-fold time reduction. During the retrieval processes, two kinds of retrieval results, i.e., baseline CTP and retrieved CTP, are provided. The baseline CTP is derived without considering in-cloud photon penetration, and the retrieved CTP is derived by solving the analytic equation, taking into consideration the in-cloud and below-cloud interactions. The retrieved CTP for the oxygen A and B bands are smaller than their related baseline CTP. At the same time, both baseline CTP and retrieved CTP at the oxygen B-band are obviously larger than those at the oxygen A-band. Compared to the difference of baseline CTP between the B-band and A-band, the difference of retrieved CTP between these two bands is generally reduced.

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Cloud vertical structure over a tropical station obtained using long-term high resolution Radiosonde measurements

10.5194/acp-2018-194 ◽

2018 ◽

Author(s):

Nelli Narendra Reddy ◽

Madineni Venkat Ratnam ◽

Ghouse Basha ◽

Varaha Ravikiran

Keyword(s):

Large Scale ◽

Vertical Structure ◽

Lower Layer ◽

Monsoon Season ◽

Single Layer ◽

Cloud Base ◽

High Level ◽

Tropical Station ◽

Layer Cloud

Abstract. Cloud vertical structure, including top and base altitudes, thickness of cloud layers, and the vertical distribution of multi-layer clouds affects the large-scale atmosphere circulation by altering gradients in the total diabatic heating/cooling and latent heat release. In this study, long-term (11 years) observations of high vertical resolution radiosondes are used to obtain the cloud vertical structure over a tropical station, Gadanki (13.5° N, 79.2° E), India. The detected cloud layers are verified with independent observations using cloud particle sensor (CPS) sonde launched from the same station. High-level clouds account for 69.05 %, 58.49 %, 55.5 %, and 58.6 % of all clouds during pre-monsoon, monsoon, post-monsoon, and winter seasons, respectively. The average cloud base (cloud top) altitude for low-level, middle-level, high-level and deep convective clouds are 1.74 km (3.16 km), 3.59 km (5.55 km), 8.79 km (10.49 km), and 1.22 km (11.45 km), respectively. Single-layer, two-layer, and three-layer clouds account for 40.80 %, 30.71 %, and 19.68 % of all cloud configurations, respectively. Multi-layer clouds occurred more frequently during the monsoon with 34.58 %. Maximum cloud top altitude and the cloud thickness occurred during monsoon season for single-layer clouds and the uppermost layer of multiple layer cloud configurations. In multi-layer cloud configurations, diurnal variations in the thickness of upper layer clouds are larger than those of lower layer clouds. Heating/cooling in the troposphere and lower stratosphere due to these clouds layers is also investigated and found peak cooling (peak warming) below (above) the Cold Point Tropopause (CPT) altitude. The magnitude of cooling (warming) increases from single-layer to four or more-layer cloud occurrence. Further, the vertical structure of clouds is also studied with respect to the arrival date of Indian summer monsoon over Gadanki.

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MODIS Global Cloud-Top Pressure and Amount Estimation: Algorithm Description and Results

Journal of Applied Meteorology and Climatology ◽

10.1175/2007jamc1705.1 ◽

2008 ◽

Vol 47 (4) ◽

pp. 1175-1198 ◽

Cited By ~ 197

Author(s):

W. Paul Menzel ◽

Richard A. Frey ◽

Hong Zhang ◽

Donald P. Wylie ◽

Chris C. Moeller ◽

...

Keyword(s):

Spatial Resolution ◽

Single Layer ◽

Estimation Algorithm ◽

Spectral Coverage ◽

Earth Observing System ◽

Cloud Properties ◽

True Location ◽

Moderate Resolution Imaging Spectroradiometer ◽

Cloud Top Pressure ◽

Layer Cloud

Abstract The Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Earth Observing System (EOS) Terra and Aqua platforms provides unique measurements for deriving global and regional cloud properties. MODIS has spectral coverage combined with spatial resolution in key atmospheric bands, which is not available on previous imagers and sounders. This increased spectral coverage/spatial resolution, along with improved onboard calibration, enhances the capability for global cloud property retrievals. MODIS operational cloud products are derived globally at spatial resolutions of 5 km (referred to as level-2 products) and are aggregated to a 1° equal-angle grid (referred to as level-3 product), available for daily, 8-day, and monthly time periods. The MODIS cloud algorithm produces cloud-top pressures that are found to be within 50 hPa of lidar determinations in single-layer cloud situations. In multilayer clouds, where the upper-layer cloud is semitransparent, the MODIS cloud pressure is representative of the radiative mean between the two cloud layers. In atmospheres prone to temperature inversions, the MODIS cloud algorithm places the cloud above the inversion and hence is as much as 200 hPa off its true location. The wealth of new information available from the MODIS operational cloud products offers the promise of improved cloud climatologies. This paper 1) describes the cloud-top pressure and amount algorithm that has evolved through collection 5 as experience has been gained with in-flight data from NASA Terra and Aqua platforms; 2) compares the MODIS cloud-top pressures, converted to cloud-top heights, with similar measurements from airborne and space-based lidars; and 3) introduces global maps of MODIS and High Resolution Infrared Sounder (HIRS) cloud-top products.

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Cloud vertical structure over a tropical station obtained using long-term high-resolution radiosonde measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-11709-2018 ◽

2018 ◽

Vol 18 (16) ◽

pp. 11709-11727 ◽

Cited By ~ 11

Author(s):

Nelli Narendra Reddy ◽

Madineni Venkat Ratnam ◽

Ghouse Basha ◽

Varaha Ravikiran

Keyword(s):

Large Scale ◽

Vertical Structure ◽

Lower Layer ◽

Single Layer ◽

Cloud Base ◽

Heating And Cooling ◽

High Level ◽

Tropical Station ◽

Layer Cloud

Abstract. Cloud vertical structure, including top and base altitudes, thickness of cloud layers, and the vertical distribution of multilayer clouds, affects large-scale atmosphere circulation by altering gradients in the total diabatic heating and cooling and latent heat release. In this study, long-term (11 years) observations of high-vertical-resolution radiosondes are used to obtain the cloud vertical structure over a tropical station at Gadanki (13.5∘ N, 79.2∘ E), India. The detected cloud layers are verified with independent observations using cloud particle sensor (CPS) sonde launched from the same station. High-level clouds account for 69.05 %, 58.49 %, 55.5 %, and 58.6 % of all clouds during the pre-monsoon, monsoon, post-monsoon, and winter seasons, respectively. The average cloud base (cloud top) altitudes for low-level, middle-level, high-level, and deep convective clouds are 1.74 km (3.16 km), 3.59 km (5.55 km), 8.79 km (10.49 km), and 1.22 km (11.45 km), respectively. Single-layer, two-layer, and three-layer clouds account for 40.80 %, 30.71 %, and 19.68 % of all cloud configurations, respectively. Multilayer clouds occurred more frequently during the monsoon with 34.58 %. Maximum cloud top altitude and cloud thickness occurred during the monsoon season for single-layer clouds and the uppermost layer of multiple-layer cloud configurations. In multilayer cloud configurations, diurnal variations in the thickness of upper-layer clouds are larger than those of lower-layer clouds. Heating and cooling in the troposphere and lower stratosphere due to these cloud layers are also investigated and peak cooling (peak warming) is found below (above) the cold-point tropopause (CPT) altitude. The magnitude of cooling (warming) increases from single-layer to four- or more-layer cloud occurrence. Further, the vertical structure of clouds is also studied with respect to the arrival date of the Indian summer monsoon over Gadanki.

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Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Atmospheric Measurement Techniques ◽

10.5194/amt-5-1889-2012 ◽

2012 ◽

Vol 5 (8) ◽

pp. 1889-1910 ◽

Cited By ~ 50

Author(s):

C. A. Poulsen ◽

R. Siddans ◽

G. E. Thomas ◽

A. M. Sayer ◽

R. G. Grainger ◽

...

Keyword(s):

Optical Depth ◽

Single Layer ◽

Optimal Estimation ◽

Product Evaluation ◽

Effective Radius ◽

Radiation Budget ◽

Physical Parameters ◽

Infrared Measurements ◽

Cloud Top Pressure ◽

Layer Cloud

Abstract. Clouds play an important role in balancing the Earth's radiation budget. Hence, it is vital that cloud climatologies are produced that quantify cloud macro and micro physical parameters and the associated uncertainty. In this paper, we present an algorithm ORAC (Oxford-RAL retrieval of Aerosol and Cloud) which is based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared, thereby ensuring that the resulting cloud properties provide both a good representation of the short-wave and long-wave radiative effects of the observed cloud. The advantages of the optimal estimation method are that it enables rigorous error propagation and the inclusion of all measurements and any a priori information and associated errors in a rigorous mathematical framework. The algorithm provides a measure of the consistency between retrieval representation of cloud and satellite radiances. The cloud parameters retrieved are the cloud top pressure, cloud optical depth, cloud effective radius, cloud fraction and cloud phase. The algorithm can be applied to most visible/infrared satellite instruments. In this paper, we demonstrate the applicability to the Along-Track Scanning Radiometers ATSR-2 and AATSR. Examples of applying the algorithm to ATSR-2 flight data are presented and the sensitivity of the retrievals assessed, in particular the algorithm is evaluated for a number of simulated single-layer and multi-layer conditions. The algorithm was found to perform well for single-layer cloud except when the cloud was very thin; i.e., less than 1 optical depths. For the multi-layer cloud, the algorithm was robust except when the upper ice cloud layer is less than five optical depths. In these cases the retrieved cloud top pressure and cloud effective radius become a weighted average of the 2 layers. The sum of optical depth of multi-layer cloud is retrieved well until the cloud becomes thick, greater than 50 optical depths, where the cloud begins to saturate. The cost proved a good indicator of multi-layer scenarios. Both the retrieval cost and the error need to be considered together in order to evaluate the quality of the retrieval. This algorithm in the configuration described here has been applied to both ATSR-2 and AATSR visible and infrared measurements in the context of the GRAPE (Global Retrieval and cloud Product Evaluation) project to produce a 14 yr consistent record for climate research.

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Stereoselectivity in Atmospheric Autoxidation

10.5194/egusphere-egu2020-6719 ◽

2020 ◽

Author(s):

Kristian H. Møller ◽

Eric Praske ◽

Lu Xu ◽

John D. Crounse ◽

Kelvin H. Bates ◽

...

Keyword(s):

Transport Model ◽

Theoretical Calculations ◽

Peroxy Radical ◽

Rate Coefficients ◽

Large Set ◽

Atmospheric Conditions ◽

Hydrogen Shift ◽

The Difference ◽

Shift Reaction ◽

High Level

<p>The importance of peroxy radical hydrogen shift reactions in the atmosphere has gained acceptance in recent years. Recent theoretical calculations have suggested that these can be stereoselective i.e. that different stereoisomers react with significantly different rate coefficients. Combining experiments (GC-CIMS) with high-level calculations (MC-TST), we show that two hydroxy peroxy radical diastereomers formed in the oxidation of crotonaldehyde have rate coefficients for their peroxy radical hydrogen shift reactions that differ by more than a factor of 10. The difference is large enough that under urban atmospheric conditions, one diastereomer would react primarily by the unimolecular H-shift, while the other would react mainly by bimolecular reactions leading to diastreomeric enhancement of the products.</p><p>For a large set of peroxy radical hydrogen shift reactions in the oxidation of isoprene, the stereospecific rate coefficients are calculated to assess the global importance of this phenomenon in the atmosphere. &#160;These calculated rate coefficients are implemented into the global chemistry-transport model GEOS-Chem to model the effect. Results show that more than 30 % of all isoprene molecules emitted undergo a minimum of one peroxy radical hydrogen shift reaction during its oxidation. Furthermore, the results show that the different diastereomers may react with rate coefficients differing by up to almost a factor of 1000, highlighting how important it is to account for this phenomenon.</p>

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Difference of [Ca2+]i Movements in Platelets Stimulated by Thrombin and TRAP: the Involvement of αIIbβ3-Mediated TXA2 Synthesis

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615038 ◽

1998 ◽

Vol 79 (06) ◽

pp. 1184-1190 ◽

Cited By ~ 19

Author(s):

Yoshiaki Tomiyama ◽

Shigenori Honda ◽

Kayoko Senzaki ◽

Akito Tanaka ◽

Mitsuru Okubo ◽

...

Keyword(s):

Platelet Aggregation ◽

Fibrinogen Binding ◽

Adp Release ◽

The Difference ◽

Txa2 Receptor Antagonist ◽

High Level ◽

Inhibition Studies ◽

Peak Increase ◽

Second Peak ◽

Assay Conditions

SummaryThis study investigated the difference of [Ca2+]i movement in platelets in response to thrombin and TRAP. The involvement of αIIbβ3 in this signaling was also studied. Stimulation of platelets with thrombin at 0.03 U/ml caused platelet aggregation and a two-peak increase in [Ca2+]i. The second peak of [Ca2+]i, but not the first peak was abolished by the inhibition of platelet aggregation with αIIbβ3 antagonists or by scavenging endogenous ADP with apyrase. A cyclooxygenase inhibitor, aspirin, and a TXA2 receptor antagonist, BM13505, also abolished the second peak of [Ca2+]i but not the first peak, although these regents did not inhibit aggregation. Under the same assay conditions, measurement of TXB2 demonstrated that αIIbβ3 antagonists and aspirin almost completely inhibited the production of TXB2. In contrast to thrombin-stimulation, TRAP caused only a single peak of [Ca2+]i even in the presence of platelet aggregation, and a high level of [Ca2+]i increase was needed for the induction of platelet aggregation. The inhibition of aggregation with αIIbβ3 antagonists had no effect on [Ca2+]i change and TXB2 production induced by TRAP. Inhibition studies using anti-GPIb antibodies suggested that GPIb may be involved in the thrombin response, but not in the TRAP. Our findings suggest that low dose thrombin causes a different [Ca2+]i response and TXA2 producing signal from TRAP. Endogenous ADP release and fibrinogen binding to αIIbβ3 are responsible for the synthesis of TXA2 which results in the induction of the second peak of [Ca2+]i in low thrombin- but not TRAP-stimulated platelets.

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ATTITUDE TO OPEN ACCESS IN RUSSIAN SCHOLARLY COMMUNITY: 2018. SURVEY RESULTS AND ANALYSIS

Scholarly Research and Information ◽

10.24108/2658-3143-2018-1-1-6-21 ◽

2018 ◽

Vol 1 (1) ◽

pp. 6-21 ◽

Cited By ~ 2

Author(s):

I. K. Razumova ◽

N. N. Litvinova ◽

M. E. Shvartsman ◽

A. Yu. Kuznetsov

Keyword(s):

Open Access ◽

Open Access Publishing ◽

Scholarly Community ◽

Research Areas ◽

Survey Results ◽

The Difference ◽

Policies And Programs ◽

The Uk ◽

High Level ◽

Access Policies

Introduction. The paper presents survey results on the awareness towards and practice of Open Access scholarly publishing among Russian academics.Materials and Methods. We employed methods of statistical analysis of survey results. Materials comprise results of data processing of Russian survey conducted in 2018 and published results of the latest international surveys. The survey comprised 1383 respondents from 182 organizations. We performed comparative studies of the responses from academics and research institutions as well as different research areas. The study compares results obtained in Russia with the recently published results of surveys conducted in the United Kingdom and Europe.Results. Our findings show that 95% of Russian respondents support open access, 94% agree to post their publications in open repositories and 75% have experience in open access publishing. We did not find any difference in the awareness and attitude towards open access among seven reference groups. Our analysis revealed the difference in the structure of open access publications of the authors from universities and research institutes. Discussion andConclusions. Results reveal a high level of awareness and support to open access and succeful practice in the open access publications in the Russian scholarly community. The results for Russia demonstrate close similarity with the results of the UK academics. The governmental open access policies and programs would foster the practical realization of the open access in Russia.

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Quantitative indicators of air traffic controllers’ attitude to the danger of errors

Science, technologies, innovation ◽

10.35668/2520-6524-2020-4-07 ◽

2020 ◽

pp. 68-78

Author(s):

O. M. Reva ◽

V. V. Kamyshin ◽

S. P. Borsuk ◽

V. A. Shulhin ◽

A. V. Nevynitsyn

Keyword(s):

Human Factor ◽

Differential Method ◽

Air Traffic ◽

Professional Activity ◽

Aviation Accidents ◽

Air Traffic Controllers ◽

The Difference ◽

Level Of Significance ◽

The Individual ◽

High Level

The negative and persistent impact of the human factor on the statistics of aviation accidents and serious incidents makes proactive studies of the attitude of “front line” aviation operators (air traffic controllers, flight crewmembers) to dangerous actions or professional conditions as a key component of the current paradigm of ICAO safety concept. This “attitude” is determined through the indicators of the influence of the human factor on decision-making, which also include the systems of preferences of air traffic controllers on the indicators and characteristics of professional activity, illustrating both the individual perception of potential risks and dangers, and the peculiarities of generalized group thinking that have developed in a particular society. Preference systems are an ordered (ranked) series of n = 21 errors: from the most dangerous to the least dangerous and characterize only the danger preference of one error over another. The degree of this preference is determined only by the difference in the ranks of the errors and does not answer the question of how much time one error is more dangerous in relation to another. The differential method for identifying the comparative danger of errors, as well as the multistep technology for identifying and filtering out marginal opinions were applied. From the initial sample of m = 37 professional air traffic controllers, two subgroups mB=20 and mG=7 people were identified with statisti-cally significant at a high level of significance within the group consistency of opinions a = 1%. Nonpara-metric optimization of the corresponding group preference systems resulted in Kemeny’s medians, in which the related (middle) ranks were missing. Based on these medians, weighted coefficients of error hazards were determined by the mathematical prioritization method. It is substantiated that with the ac-cepted accuracy of calculations, the results obtained at the second iteration of this method are more ac-ceptable. The values of the error hazard coefficients, together with their ranks established in the preference systems, allow a more complete quantitative and qualitative analysis of the attitude of both individual air traffic controllers and their professional groups to hazardous actions or conditions.

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A Fast Retrieval of Cloud Parameters Using a Triplet of Wavelengths of Oxygen Dimer Band around 477 nm

Remote Sensing ◽

10.3390/rs13010152 ◽

2021 ◽

Vol 13 (1) ◽

pp. 152

Author(s):

Haklim Choi ◽

Xiong Liu ◽

Gonzalo Gonzalez Abad ◽

Jongjin Seo ◽

Kwang-Mog Lee ◽

...

Keyword(s):

Scattered Light ◽

Trace Gas ◽

Retrieval Algorithm ◽

The Novel ◽

Cloud Parameters ◽

Retrieval Scheme ◽

The Difference ◽

The Look ◽

Time Required ◽

Cloud Top Pressure

Clouds act as a major reflector that changes the amount of sunlight reflected to space. Change in radiance intensity due to the presence of clouds interrupts the retrieval of trace gas or aerosol properties from satellite data. In this paper, we developed a fast and robust algorithm, named the fast cloud retrieval algorithm, using a triplet of wavelengths (469, 477, and 485 nm) of the O2–O2 absorption band around 477 nm (CLDTO4) to derive the cloud information such as cloud top pressure (CTP) and cloud fraction (CF) for the Geostationary Environment Monitoring Spectrometer (GEMS). The novel algorithm is based on the fact that the difference in the optical path through which light passes with regard to the altitude of clouds causes a change in radiance due to the absorption of O2–O2 at the three selected wavelengths. To reduce the time required for algorithm calculations, the look-up table (LUT) method was applied. The LUT was pre-constructed for various conditions of geometry using Vectorized Linearized Discrete Ordinate Radiative Transfer (VLIDORT) to consider the polarization of the scattered light. The GEMS was launched in February 2020, but the observed data of GEMS have not yet been widely released. To evaluate the performance of the algorithm, the retrieved CTP and CF using observational data from the Global Ozone Monitoring Experiment-2 (GOME-2), which cover the spectral range of GEMS, were compared with the results of the Fast Retrieval Scheme for Clouds from the Oxygen A band (FRESCO) algorithm, which is based on the O2 A-band. There was good agreement between the results, despite small discrepancies for low clouds.

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