scholarly journals Detection of thin cirrus from 1.38 μm/0.65 μm reflectance ratio combined with 8.6–11 μm brightness temperature difference

2003 ◽  
Vol 30 (19) ◽  
Author(s):  
J. K. Roskovensky
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Reflectance Ratio

scholarly journals Microwave signatures of ice hydrometeors from ground-based observations above Summit, Greenland

2015 ◽  
Vol 15 (23) ◽  
pp. 34497-34532
Author(s):  
C. Pettersen ◽  
R. Bennartz ◽  
M. S. Kulie ◽  
A. J. Merrelli ◽  
M. D. Shupe ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Liquid Water ◽  
High Frequency ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radar ◽  
Brightness Temperatures ◽  
High Frequency Microwave

Abstract. Multi-instrument, ground-based measurements provide unique and comprehensive datasets of the atmosphere for a specific location over long periods of time and resulting data compliments past and existing global satellite observations. This paper explores the effect of ice hydrometeors on ground-based, high frequency passive microwave measurements and attempts to isolate an ice signature for summer seasons at Summit, Greenland from 2010–2013. Data from a combination of passive microwave, cloud radar, radiosonde, and ceilometer were examined to isolate the ice signature at microwave wavelengths. By limiting the study to a cloud liquid water path of 40 g m−2 or less, the cloud radar can identify cases where the precipitation was dominated by ice. These cases were examined using liquid water and gas microwave absorption models, and brightness temperatures were calculated for the high frequency microwave channels: 90, 150, and 225 GHz. By comparing the measured brightness temperatures from the microwave radiometers and the calculated brightness temperature using only gas and liquid contributions, any residual brightness temperature difference is due to emission and scattering of microwave radiation from the ice hydrometeors in the column. The ice signature in the 90, 150, and 225 GHz channels for the Summit Station summer months was isolated. This measured ice signature was then compared to an equivalent brightness temperature difference calculated with a radiative transfer model including microwave single scattering properties for several ice habits. Initial model results compare well against the four years of summer season isolated ice signature in the high-frequency microwave channels.

Application of nighttime fog detection method using MSG8 SEVIRI in an arid environment

2020 ◽  
Author(s):  
Michael Weston ◽  
Marouane Temimi
Keyword(s):  
Brightness Temperature ◽  
United Arab Emirates ◽  
Temperature Difference ◽  
Land Surface ◽  
Visual Inspection ◽  
Detection Method ◽  
Arid Environment ◽  
Desert Region ◽  
Channel Ratio ◽  
Low Cloud

<p class="western"><span>The detection of fog and low cloud (FLC) from satellite data remains challenging despite advances in methodologies and technology. Current methods make use of one or a combination of channel differencing from satellite instruments, surface observations, model data or artificial intelligence. An alternative to the brightness temperature difference method was developed for the GOES-R advanced baseline imager (ABI) which makes use of a channel ratio instead of a channel difference. We apply this method, the so called pseudo emissivity of the 3.9 µm channel, to SEVIRI MSG8 data over the United Arab Emirates, a desert region of the Arabian Peninsula. Low cloud is removed using temperature difference between ERA5 land surface temperature and 10.8 µm channel brightness temperature. Visual inspection of the final fog only mask shows that this method works well over this region. Verification at three sites where METAR data is available returned POD (FAR) of 0.77 (0.27), 0.50 (0.65) and 0.83 (0.26) respectively. Application of this method can be further developed to represent seasonal fog distribution and frequency across the United Arab Emirates.</span></p>

scholarly journals DECISION TREE CLOUD DETECTION ALGORITHM BASED ON FY-4A SATELLITE DATA

2019 ◽  
Vol XLII-3/W9 ◽  
pp. 219-226
Author(s):  
Z. F. Yu ◽  
W. H. Ai ◽  
Z. H. Tan ◽  
W. Yan
Keyword(s):  
Decision Tree ◽  
Brightness Temperature ◽  
Temperature Difference ◽  
Satellite Data ◽  
Detection Algorithm ◽  
Processing Technology ◽  
Cloud Detection ◽  
Detection Model ◽  
Meteorological Satellite

Abstract. In order to study the on-board processing technology of meteorological satellites, a decision tree cloud detection algorithm is proposed by taking FY-4A satellite data as an example. According to the channel setting of the Advanced Geosynchronous Radiation Imager (AGRI) on FY-4A satellite, the 0.65 μm, 1.375 μm, 3.75 μm, and 10.7 μm bands are selected as the cloud detection channels, and the reflectance, brightness temperature or bright temperature difference of the four channels are used as the cloud detection indicators, the thresholds of the four cloud detection indicators are obtained through statistics. On this basis, the decision tree cloud detection model is constructed and validated using FY-4A satellite data. The results show that the algorithm is simple, convenient and efficient, and the overall effect of cloud detection is good. It is an effective way for meteorological satellite cloud detection on-board processing technology.

Bispectral and brightness temperature difference analysis of 1991 FIRE cirrus IFO satellite data

1993 ◽  
Author(s):  
Eric O. Schmidt ◽  
Robert F. Arduini ◽  
Bruce A. Wielicki ◽  
Bryan A. Baum
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Satellite Data ◽  
Difference Analysis

Evaluation of AIRS, MODIS, and HIRS 11 micron brightness temperature difference changes from 2002 through 2006

2006 ◽  
Author(s):  
Steven E. Broberg ◽  
Hartmut H. Aumann ◽  
David T. Gregorich ◽  
X. Xiong
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference

scholarly journals Analisis Tailwind Penyebab Go-Around pada 38 Bandara di Indonesia dalam Periode Januari-Februari 2020

2020 ◽  
Vol 32 (2) ◽  
Author(s):  
Achmad Fahruddin Rais ◽  
Bambang Wijayanto ◽  
Erika Meinovelia
Keyword(s):  
Brightness Temperature ◽  
Satellite Imagery ◽  
Temperature Difference ◽  
High Speed ◽  
Lower Troposphere ◽  
Wind Gust ◽  
Surface Observation

Studi ini berfokus pada analisis tailwind penyebab go-around pada 38 bandara di Indonesia dalam periode Januari-Februari 2020. Dalam studi ini dilakukan perbandingan tailwind laporan pilot, tailwind observasi permukaan (10 m), dan tailwind pada ketinggian 1000 ft untuk mengetahui akurasi tailwind yang dilaporkan oleh pilot. Literatur menyebutkan bahwa angin kecepatan tinggi di troposfer bawah berkaitan dengan wind gust yang berasal dari awan cumulonimbus (Cb). Dengan dasar tersebut maka dilakukan analisis perbandingan laporan pilot terhadap keberadaan awan Cb sampai sejauh 40 km dari runway in use dengan menggunakan kombinasi kriteria brightness temperature difference (BTD) kanal IR1-IR2 dan brightness temperature (BT) kanal IR1 citra satelit Himawari-8. Hasil penelitian menunjukkan bahwa tailwind laporan pilot lebih besar daripada tailwind angin permukaan dan 1000 ft, serta kebanyakan tailwind laporan pilot tersebut berkaitan dengan potensi wind gust yang muncul dari awan Cb baik di sekitar atau di luar runway.Kata kunci: Cumulonimbus, go-around, tailwind, wind gust. AbstractAn Analysis of Go-Around-Causing Tailwind at 38 Airports in Indonesia in the Period of January-February 2020: This study focused on analyzing the tailwind that causing go-around at 38 airports in Indonesia in the period of January to February 2020. We made a tailwind comparison of the pilot report, surface observation (10 m), and observation of 1000 ft to determine the accuracy of the tailwind reported by the pilot. The literature stated that high-speed winds in the lower troposphere were related to wind gust coming from cumulonimbus (Cb) clouds, so we compared pilot report to the presence of Cb clouds as far as 40 km from the runway in use by using a combination of brightness temperature difference (BTD) IR1-IR2 channels and brightness temperature (BT) IR1 channel of Himawari-8 satellite imagery. The results showed that the tailwind of the pilot report was larger than the tailwind of surface and 1000 ft observations and most of the tailwind was related to the potential wind gust that emerged from the Cb clouds either around or outside the runway.Keywords: Cumulonimbus, go-around, tailwind, wind gust.

scholarly journals Stratospheric water vapour budget and convection overshooting the tropopause: modelling study from SCOUT-AMMA

2010 ◽  
Vol 10 (17) ◽  
pp. 8267-8286 ◽  
Author(s):  
X. M. Liu ◽  
E. D. Rivière ◽  
V. Marécal ◽  
G. Durry ◽  
A. Hamdouni ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Water Vapour ◽  
Temperature Difference ◽  
Water Distribution ◽  
Lower Stratosphere ◽  
Background Level ◽  
Convective System ◽  
Regional Atmospheric Modelling System ◽  
Initial Location ◽  
The Impact

Abstract. The aim of this paper is to study the impacts of overshooting convection at a local scale on the water distribution in the tropical UTLS. Overshooting convection is assumed to be one of the processes controlling the entry of water vapour mixing ratio in the stratosphere by injecting ice crystals above the tropopause which later sublimate and hydrate the lower stratosphere. For this purpose, we quantify the individual impact of two cases of overshooting convection in Africa observed during SCOUT-AMMA: the case of 4 August 2006 over Southern Chad which is likely to have influenced the water vapour measurements by micro-SDLA and FLASH-B from Niamey on 5 August, and the case of a mesoscale convective system over Aïr on 5 August 2006. We make use of high resolution (down to 1 km horizontally) nested grid simulations with the three-dimensional regional atmospheric model BRAMS (Brazilian Regional Atmospheric Modelling System). In both cases, BRAMS succeeds in simulating the main features of the convective activity, as well as overshooting convection, though the exact position and time of the overshoots indicated by MSG brightness temperature difference is not fully reproduced (typically 1° displacement in latitude compared with the overshoots indicated by brightness temperature difference from satellite observations for both cases, and several hours shift for the Aïr case on 5 August 2006). Total water budgets associated with these two events show a significant injection of ice particles above the tropopause with maximum values of about 3.7 ton s−1 for the Chad case (4 August) and 1.4 ton s−1 for the Aïr case (5 August), and a total upward cross tropopause transport of about 3300 ton h−1 for the Chad case and 2400 ton h−1 for the Aïr case in the third domain of simulation. The order of magnitude of these modelled fluxes is lower but comparable with similar studies in other tropical areas based on models. These two estimations exhibit significant differences and highlight variability among the cases of the impact of overshooting convection in hydrating the lower stratosphere. We show that the regional enhancement of water above the tropopause is between 0.21 to 0.67 ppmv between 380 and 400 K, generally in the range of other model estimations. The amount of water which remains in the stratosphere after the overshoot is estimated for both cases. A range of 330 to 507 tons is found for the Chad case and an upper limit of 200 tons is found for the Aïr case. Finally we emphasize that the hydrated area in the LS by overshooting convection can be advected relatively far away from the overshoot initial location, with locally mixing ratios of more than 3 ppmv higher than the background level, which is compatible with the balloon borne measurements performed above Niamey in the same air mass, 30 h after the overshoot.

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