AIRS visible light channels: Lessons from 15 years of using internal calibration sources, vicarious calibration, and the use of deep convective clouds (Conference Presentation)

2017 ◽  
Author(s):  
Steven E. Broberg ◽  
Hartmut H. Aumann ◽  
Evan M. Manning
Keyword(s):  
Visible Light ◽  
Vicarious Calibration ◽  
Convective Clouds ◽  
Internal Calibration ◽  
Deep Convective Clouds

Analysis on spectral reflectivity of deep convective clouds towards vicarious calibration of UV/VIS hyperspectral instruments onboard geostationary satellites

2020 ◽  
Author(s):  
Yeeun Lee ◽  
Myoung-Hwan Ahn ◽  
Mina Kang
Keyword(s):  
Detection Method ◽  
Hyperspectral Data ◽  
Spectral Radiance ◽  
Atmospheric Effects ◽  
Detection Thresholds ◽  
Vicarious Calibration ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Deep Convective Clouds ◽  
Environmental Sensor

<p>To meet the increasing demand for obtaining reliable information on the atmospheric distribution of trace gases and aerosols, GEO-constellation consisting of Geostationary Korean Multi-Purpose Satellite-2B (GK-2B), Tropospheric Emissions: Monitoring Pollution and Sentinel-4 are planned to be operated in this decade. As one of the environmental instruments, Geostationary Environment Monitoring Spectrometer (GEMS) onboard GK-2B planned to launch in February 2020 is designed to provide spectral radiance in the wavelength range of 300-500 nm as observing the tropical western Pacific region. To prepare a means of monitoring the calibration accuracy of GEMS, we aim to evaluate the feasibility of deep convective clouds (DCCs) as a possible target for vicarious calibration of GEMS. While the DCC calibration technique has been continuously verified from various meteorological satellite programs, it has been rarely researched in the ultraviolet and visible spectral region especially for the hyperspectral data of the environmental sensor. To finely detect DCCs reflecting stable signal throughout the spectral range of GEMS, we update the DCC detection thresholds based on the conventional detection method by applying both visible and infrared detection thresholds. To examine the effectiveness of the detection, Tropospheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor is used as a proxy of GEMS. Advanced Himawari Imager onboard Himawari-8 is also used to construct the collocated data with TROPOMI since the environmental sensor only provides spectral radiance at shorter wavelengths. The DCCs detected by the updated thresholds show higher reflectivity over 0.9 as presenting homogeneous spectral features even at the Fraunhofer lines in which the atmospheric effects are prominent. Cloud properties such as the cloud optical thickness and cloud top height also become relatively homogeneous when both visible and infrared thresholds are used for the DCC detection since both radiation thresholds can be complement to limit the cloud properties of the detected clouds. With the detailed results, bidirectional reflectance distribution function (BRDF) is also to be estimated by applying the updated DCC detection method hereafter in the study.</p>

scholarly journals A New Potential of the Deep Convective Clouds as the Calibration Target for a Geostationary UV/VIS Hyperspectral Spectrometer

2019 ◽  
Author(s):  
Ye Eun Lee ◽  
Myoung-Hwan Ahn ◽  
Mina Kang
Keyword(s):  
Promising Result ◽  
Geostationary Satellite ◽  
Asia Pacific ◽  
Ozone Monitoring Instrument ◽  
Single Observation ◽  
Vicarious Calibration ◽  
Monitoring Instrument ◽  
Convective Clouds ◽  
Observation Area ◽  
Deep Convective Clouds

As one of GEO-constellation for environmental monitoring in the next decade, Geostationary Environment Monitoring Spectrometer (GEMS) is designed to observe the Asia Pacific region to provide the information on the atmospheric chemicals, aerosol and cloud properties. For the continuous monitoring of the sensor performance after its launch in early 2020, here we suggest deep convective clouds (DCCs) as a possible target for the vicarious calibration of GEMS, the first UV/VIS hyperspectral sensor onboard a geostationary satellite. Tropospheric Monitoring Instrument (TROPOMI) and Ozone Monitoring Instrument (OMI) are used as a proxy of GEMS, and a conventional DCC detection approach applying the thermal threshold test is used for the DCC detection based on the collocations with Advance Himawari-8 Imager (AHI) onboard Himawari-8 geostationary satellite. DCCs are frequently detected over the GEMS observation area on average over 200 pixels in a single observation scene. Considering the spatial resolution of GEMS, 3.5 km×7 km which is similar to TROPOMI, and its temporal resolution (8 times a day), availability of DCCs for vicarious calibration of GEMS is expected to be sufficient. Inspection of the DCC reflectivity spectra estimated from the OMI and TROPOMI data also shows a promising result. Even though, their observation geometry and sensor characteristics are quite a different, the estimated DCC spectra agree quite a well within a known uncertainty range with comparable spectral features. When the DCC detection is further improved by applying both visible and infrared tests, the variability of DCC reflectivity from the TROPOMI data is reduced by half, from 10% to 5%. This is mainly due to the efficient screening of cold thin cirrus with the visible test and of bright warm clouds with the infrared test. The precise DCC detection is also expected to contribute to the accurate characterization of the cloud reflectivity, which will be further investigated.

scholarly journals The New Potential of Deep Convective Clouds as a Calibration Target for a Geostationary UV/VIS Hyperspectral Spectrometer

2020 ◽  
Vol 12 (3) ◽  
pp. 446 ◽  
Author(s):  
Yeeun Lee ◽  
Myoung-Hwan Ahn ◽  
Mina Kang
Keyword(s):  
Geostationary Satellite ◽  
Asia Pacific ◽  
Future Research ◽  
Ozone Monitoring Instrument ◽  
Single Observation ◽  
Vicarious Calibration ◽  
Monitoring Instrument ◽  
Convective Clouds ◽  
Observation Area ◽  
Deep Convective Clouds

As one of geostationary earth orbit constellation for environmental monitoring over the next decade, the Geostationary Environment Monitoring Spectrometer (GEMS) has been designed to observe the Asia-Pacific region to provide information on atmospheric chemicals, aerosols, and cloud properties. In order to continuously monitor sensor performance after its launch in early 2020, we suggest in this paper deep convective clouds (DCCs) as a possible target for the vicarious calibration of the GEMS, the first ultraviolet and visible hyperspectral sensor onboard a geostationary satellite. The Tropospheric Monitoring Instrument (TROPOMI) and the Ozone Monitoring Instrument (OMI) are used as a proxy for GEMS, and a conventional DCC-detection approach applying a thermal threshold test is used for DCC detection based on collocations with the Advanced Himawari Imager (AHI) onboard the Himawari-8 geostationary satellite. DCCs are frequently detected over the GEMS observation area at an average of over 200 pixels within a single observation scene. Considering the spatial resolution of the GEMS (3.5 × 8 km2), which is similar to the TROPOMI and its temporal resolution (eight times a day), the availability of DCCs is expected to be sufficient for the vicarious calibration of the GEMS. Inspection of the DCC reflectivity spectra estimated from OMI and TROPOMI data also shows promising results. The estimated DCC spectra are in good agreement within a known uncertainty range with comparable spectral features even with different observation geometries and sensor characteristics. When DCC detection is improved further by applying both visible and infrared tests, the variability of DCC reflectivity from TROPOMI data is reduced from 10% to 5%. This is mainly due to the efficient screening out of cold, thin cirrus clouds in the visible test and of bright, warm clouds in the infrared test. Precise DCC detection is also expected to contribute to the accurate characterization of cloud reflectivity, which will be investigated further in future research.

Vicarious calibration of S-NPP/VIIRS day–night band using deep convective clouds

2015 ◽  
Vol 158 ◽  
pp. 42-55 ◽  
Author(s):  
Shuo Ma ◽  
Wei Yan ◽  
Yun-Xian Huang ◽  
Wei-Hua Ai ◽  
Xianbin Zhao
Keyword(s):  
Vicarious Calibration ◽  
Convective Clouds ◽  
Deep Convective Clouds

scholarly journals Frequency of deep convective clouds in the tropical zone from 10 years of AIRS data

2013 ◽  
Vol 13 (21) ◽  
pp. 10795-10806 ◽  
Author(s):  
H. H. Aumann ◽  
A. Ruzmaikin
Keyword(s):  
Brightness Temperature ◽  
Frequency Of Occurrence ◽  
Tropical Zone ◽  
Convective Clouds ◽  
The Past ◽  
Atmospheric Window ◽  
Deep Convective Clouds ◽  
Sst Anomaly ◽  
The Difference ◽  
Global Precipitation

Abstract. Deep convective clouds (DCCs) have been widely studied because of their association with heavy precipitation and severe weather events. Changes in the properties of DCCs are likely in a changing climate. Ten years of data collected by Atmospheric Infrared Sounder (AIRS) allow us to identify decadal trends in frequency of occurrence of DCCs over land and ocean. In the past, DCCs have been identified in the thermal infrared by three methods: (1) thresholds based on the absolute value of an atmospheric window channel brightness temperature; (2) thresholds based on the difference between the brightness temperature in an atmospheric window channel and the brightness temperature centered on a strong water vapor absorption line; and (3) a threshold using the difference between the window channel brightness temperature and the tropopause temperature based on climatology. Simultaneous observations of these infrared identified DCCs with the Advanced Microwave Sounding Unit–Humidity Sounder for Brazil (AMSU-HSB) using 183 GHz water channels provide a statistical correlation with microwave deep convection and overshooting convection. In the past 10 years, the frequency of occurrence of DCCs has decreased for the tropical ocean, while it has increased for tropical land. The area of the tropical zone associated with DCCs is typically much less than 1%. We find that the least frequent, more extreme DCCs show the largest trend in frequency of occurrence, increasing over land and decreasing over ocean. The trends for land and ocean closely balance, such that the DCC frequency changed at an insignificant rate for the entire tropical zone. This pattern of essentially zero trend for the tropical zone, but opposite land/ocean trends, is consistent with measurements of global precipitation. The changes in frequency of occurrence of the DCCs are correlated with the Niño34 index, which defines the sea surface temperature (SST) anomaly in the east-central Pacific. This is also consistent with patterns seen in global precipitation. This suggests that the observed changes in the frequency are part of a decadal variability characterized by shifts in the main tropical circulation patterns, which does not fully balance in the 10-year AIRS data record. The regional correlations and anti-correlations of the DCC frequency anomaly with the Multivariate ENSO Index (MEI) provide a new perspective for the regional analysis of past events, since the SST anomaly in the Nino34 region is available in the form of the extended MEI from 1871.

scholarly journals How do changes in warm-phase microphysics affect deep convective clouds?

2017 ◽  
Vol 17 (15) ◽  
pp. 9585-9598 ◽  
Author(s):  
Qian Chen ◽  
Ilan Koren ◽  
Orit Altaratz ◽  
Reuven H. Heiblum ◽  
Guy Dagan ◽  
...  
Keyword(s):  
Rain Rate ◽  
Convective Cloud ◽  
Cloud Fraction ◽  
Marshall Islands ◽  
Cloud System ◽  
Main Question ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Aerosol Effects ◽  
Deep Convective Cloud

Abstract. Understanding aerosol effects on deep convective clouds and the derived effects on the radiation budget and rain patterns can largely contribute to estimations of climate uncertainties. The challenge is difficult in part because key microphysical processes in the mixed and cold phases are still not well understood. For deep convective clouds with a warm base, understanding aerosol effects on the warm processes is extremely important as they set the initial and boundary conditions for the cold processes. Therefore, the focus of this study is the warm phase, which can be better resolved. The main question is: How do aerosol-derived changes in the warm phase affect the properties of deep convective cloud systems? To explore this question, we used a weather research and forecasting (WRF) model with spectral bin microphysics to simulate a deep convective cloud system over the Marshall Islands during the Kwajalein Experiment (KWAJEX). The model results were validated against observations, showing similarities in the vertical profile of radar reflectivity and the surface rain rate. Simulations with larger aerosol loading resulted in a larger total cloud mass, a larger cloud fraction in the upper levels, and a larger frequency of strong updrafts and rain rates. Enlarged mass both below and above the zero temperature level (ZTL) contributed to the increase in cloud total mass (water and ice) in the polluted runs. Increased condensation efficiency of cloud droplets governed the gain in mass below the ZTL, while both enhanced condensational and depositional growth led to increased mass above it. The enhanced mass loading above the ZTL acted to reduce the cloud buoyancy, while the thermal buoyancy (driven by the enhanced latent heat release) increased in the polluted runs. The overall effect showed an increased upward transport (across the ZTL) of liquid water driven by both larger updrafts and larger droplet mobility. These aerosol effects were reflected in the larger ratio between the masses located above and below the ZTL in the polluted runs. When comparing the net mass flux crossing the ZTL in the clean and polluted runs, the difference was small. However, when comparing the upward and downward fluxes separately, the increase in aerosol concentration was seen to dramatically increase the fluxes in both directions, indicating the aerosol amplification effect of the convection and the affected cloud system properties, such as cloud fraction and rain rate.

scholarly journals Vertical distribution of the phase state of particles in tropical deep-convective clouds as derived from cloud-side reflected solar radiation measurements

2017 ◽  
Author(s):  
Evelyn Jäkel ◽  
Manfred Wendisch ◽  
Trismono C. Krisna ◽  
Florian Ewald ◽  
Tobias Kölling ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Phase State ◽  
Lower Boundary ◽  
Mixed Phase ◽  
Vertical Position ◽  
Cloud Particle ◽  
Phase Layer ◽  
Spectral Reflectivity ◽  
Convective Clouds ◽  
Deep Convective Clouds

Abstract. Vertical profiles of the cloud particle phase state in tropical deep-convective clouds (DCCs) were investigated using airborne solar radiation data collected by the German research aircraft HALO during the ACRIDICON-CHUVA campaign, which was conducted over the Brazilian Amazon in September 2014. A phase discrimination retrieval based on imaging spec-troradiometer measurements of cloud side spectral reflectivity was applied to DCCs under different aerosol conditions. From the retrieval results the height of the mixed phase layer of the DCCs was determined. The retrieved profiles were compared with in situ measurements and satellite observations. It was found that the depth and vertical position of the mixed phase layer can vary up to 900 m for one single cloud scene. In particular, this variation is attributed to the different stages of cloud development in one scene. Clouds of mature or decaying stage are affected by falling ice particles resulting in lower levels of fully glaciated cloud layers compared to growing clouds. Comparing polluted and moderate aerosol conditions revealed a shift of the lower boundary of the mixed phase layer from 5.6 ± 0.2 km (269 K) [moderate] to 6.2 ± 0.3 km (267 K) [polluted], and of the upper boundary from 6.8 ± 0.2 km (263 K) [moderate] to 7.4 ± 0.4 km (259 K) [polluted], as would be expected from theory.

scholarly journals Frequency of deep convective clouds in the tropical zone from ten years of AIRS data

2013 ◽  
Vol 13 (4) ◽  
pp. 10009-10047
Author(s):  
H. H. Aumann ◽  
A. Ruzmaikin
Keyword(s):  
Water Vapor ◽  
Brightness Temperature ◽  
Frequency Of Occurrence ◽  
Tropical Zone ◽  
Convective Clouds ◽  
Atmospheric Window ◽  
Deep Convective Clouds ◽  
Sst Anomaly ◽  
The Difference ◽  
Global Precipitation

Abstract. Deep Convective Clouds (DCC) have been widely studied because of their association with heavy precipitation and severe weather events. To identify DCC with Atmospheric Infrared Sounder (AIRS) data we use three types of thresholds: (1) thresholds based on the absolute value of an atmospheric window channel brightness temperature; (2) thresholds based on the difference between the brightness temperature in an atmospheric window channel and the brightness temperature centered on a strong water vapor absorption line; and (3) a threshold using the difference between the window channel brightness temperature and the tropopause temperature based on climatology. We find that DCC identified with threshold (2) (referred to as DCCw4) cover 0.16% of the area of the tropical zone and 72% of them are identified as deep convective, 39% are overshooting based on simultaneous observations with the Advanced Microwave Sounding Unit-HSB (AMSU-HSB) 183 GHz water vapor channels. In the past ten years the frequency of occurrence of DCC decreased for the tropical ocean, while it increased for tropical land. The land increase-ocean decrease closely balance, such that the DCC frequency changed at an insignificant rate for the entire tropical zone. This pattern of essentially zero trend for the tropical zone, but opposite land/ocean trends, is consistent with measurements of global precipitation. The changes in frequency of occurrence of the DCC are correlated with the Niño34 index, which defines the SST anomaly in the East-Central Pacific. This is also consistent with patterns seen in global precipitation. This suggests that the observed changes in the frequency are part of a decadal variability characterized by shifts in the main tropical circulation patterns, which does not fully balance in the ten year AIRS data record. The regional correlations and anti-correlations of the DCC frequency anomaly with the Multivariate ENSO Index (MEI) provides a new perspective for the regional analysis of past events, since the SST anomaly in the Nino34 region is available in the form of the extended MEI since 1871. Depending on the selected threshold, the frequency of DCC in the tropical zone ranges from 0.06% to 0.8% of the area. We find that the least frequent, more extreme DCC also show the largest trend in frequency, increasing over land, decreasing over ocean. This finding fits into the framework of how weather extremes respond to climate change.

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