Evaluating the diurnal cycle in cloud top temperature from SEVIRI
The variability of convective cloud spans a wide range of temporal and spatial scales and is of fundamental importance for global weather and climate systems. Datasets from geostationary satellite instruments such as the Spinning Enhanced Visible and Infrared Imager (SEVIRI) provide high-time-res...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/7035/2017/acp-17-7035-2017.pdf |
| _version_ | 1819261124606951424 |
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| author | S. Taylor P. Stier B. White S. Finkensieper M. Stengel |
| author_facet | S. Taylor P. Stier B. White S. Finkensieper M. Stengel |
| author_sort | S. Taylor |
| collection | DOAJ |
| description | The variability of convective cloud spans a wide range of temporal
and spatial scales and is of fundamental importance for global weather and
climate systems. Datasets from geostationary satellite instruments such as
the Spinning Enhanced Visible and Infrared Imager (SEVIRI) provide high-time-resolution observations across a large area. In this
study we use data from SEVIRI to quantify the diurnal cycle of cloud top
temperature within the instrument's field of view and discuss these results
in relation to retrieval biases.
<br><br>
We evaluate SEVIRI cloud top temperatures from the new CLAAS-2 (CLoud
property dAtAset using SEVIRI, Edition 2) dataset against Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data.
Results show a mean bias of +0.44 K with a standard deviation of 11.7 K, which is in agreement with previous validation studies. Analysis of
the spatio-temporal distribution of these errors shows that absolute retrieval
biases vary from less than 5 K over the southeast Atlantic Ocean up to
30 K over central Africa at night. Night- and daytime retrieval biases
can also differ by up to 30 K in some areas, potentially contributing
to biases in the estimated amplitude of the diurnal cycle. This illustrates
the importance of considering spatial and diurnal variations in retrieval
errors when using the CLAAS-2 dataset.
<br><br>
Keeping these biases in mind, we quantify the seasonal, diurnal, and spatial
variation of cloud top temperature across SEVIRI's field of view using the
CLAAS-2 dataset. By comparing the mean diurnal cycle of cloud top temperature
with the retrieval bias, we find that diurnal variations in the retrieval bias
can be small but are often of the same order of magnitude as the amplitude
of the observed diurnal cycle, indicating that in some regions the diurnal
cycle apparent in the observations may be significantly impacted by diurnal
variability in the accuracy of the retrieval.
<br><br>
We show that the CLAAS-2 dataset can measure the diurnal cycle of cloud tops
accurately in regions of stratiform cloud such as the southeast Atlantic
Ocean and Europe, where cloud top temperature retrieval biases are small and
exhibit limited spatial and temporal variability. Quantifying the diurnal
cycle over the tropics and regions of desert is more difficult, as retrieval
biases are larger and display significant diurnal variability. CLAAS-2 cloud
top temperature data are found to be of limited skill in measuring the
diurnal cycle accurately over desert regions. In tropical regions such as
central Africa, the diurnal cycle can be described by the CLAAS-2 data to
some extent, although retrieval biases appear to reduce the amplitude of the
real diurnal cycle of cloud top temperatures.
<br><br>
This is the first study to relate the diurnal variations in SEVIRI retrieval
bias to observed diurnal cycles in cloud top temperature. Our results may be
of interest to those in the observation and modelling communities when using
cloud top properties data from SEVIRI, particularly for studies considering
the diurnal cycle of convection. |
| first_indexed | 2024-12-23T19:36:49Z |
| format | Article |
| id | doaj.art-7957b11305e740c8851804eabcb7606d |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-23T19:36:49Z |
| publishDate | 2017-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-7957b11305e740c8851804eabcb7606d2022-12-21T17:33:46ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-06-01177035705310.5194/acp-17-7035-2017Evaluating the diurnal cycle in cloud top temperature from SEVIRIS. Taylor0P. Stier1B. White2S. Finkensieper3M. Stengel4Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UKAtmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UKAtmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UKDeutscher Wetterdienst (DWD), Offenbach, GermanyDeutscher Wetterdienst (DWD), Offenbach, GermanyThe variability of convective cloud spans a wide range of temporal and spatial scales and is of fundamental importance for global weather and climate systems. Datasets from geostationary satellite instruments such as the Spinning Enhanced Visible and Infrared Imager (SEVIRI) provide high-time-resolution observations across a large area. In this study we use data from SEVIRI to quantify the diurnal cycle of cloud top temperature within the instrument's field of view and discuss these results in relation to retrieval biases. <br><br> We evaluate SEVIRI cloud top temperatures from the new CLAAS-2 (CLoud property dAtAset using SEVIRI, Edition 2) dataset against Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data. Results show a mean bias of +0.44 K with a standard deviation of 11.7 K, which is in agreement with previous validation studies. Analysis of the spatio-temporal distribution of these errors shows that absolute retrieval biases vary from less than 5 K over the southeast Atlantic Ocean up to 30 K over central Africa at night. Night- and daytime retrieval biases can also differ by up to 30 K in some areas, potentially contributing to biases in the estimated amplitude of the diurnal cycle. This illustrates the importance of considering spatial and diurnal variations in retrieval errors when using the CLAAS-2 dataset. <br><br> Keeping these biases in mind, we quantify the seasonal, diurnal, and spatial variation of cloud top temperature across SEVIRI's field of view using the CLAAS-2 dataset. By comparing the mean diurnal cycle of cloud top temperature with the retrieval bias, we find that diurnal variations in the retrieval bias can be small but are often of the same order of magnitude as the amplitude of the observed diurnal cycle, indicating that in some regions the diurnal cycle apparent in the observations may be significantly impacted by diurnal variability in the accuracy of the retrieval. <br><br> We show that the CLAAS-2 dataset can measure the diurnal cycle of cloud tops accurately in regions of stratiform cloud such as the southeast Atlantic Ocean and Europe, where cloud top temperature retrieval biases are small and exhibit limited spatial and temporal variability. Quantifying the diurnal cycle over the tropics and regions of desert is more difficult, as retrieval biases are larger and display significant diurnal variability. CLAAS-2 cloud top temperature data are found to be of limited skill in measuring the diurnal cycle accurately over desert regions. In tropical regions such as central Africa, the diurnal cycle can be described by the CLAAS-2 data to some extent, although retrieval biases appear to reduce the amplitude of the real diurnal cycle of cloud top temperatures. <br><br> This is the first study to relate the diurnal variations in SEVIRI retrieval bias to observed diurnal cycles in cloud top temperature. Our results may be of interest to those in the observation and modelling communities when using cloud top properties data from SEVIRI, particularly for studies considering the diurnal cycle of convection.http://www.atmos-chem-phys.net/17/7035/2017/acp-17-7035-2017.pdf |
| spellingShingle | S. Taylor P. Stier B. White S. Finkensieper M. Stengel Evaluating the diurnal cycle in cloud top temperature from SEVIRI Atmospheric Chemistry and Physics |
| title | Evaluating the diurnal cycle in cloud top temperature from SEVIRI |
| title_full | Evaluating the diurnal cycle in cloud top temperature from SEVIRI |
| title_fullStr | Evaluating the diurnal cycle in cloud top temperature from SEVIRI |
| title_full_unstemmed | Evaluating the diurnal cycle in cloud top temperature from SEVIRI |
| title_short | Evaluating the diurnal cycle in cloud top temperature from SEVIRI |
| title_sort | evaluating the diurnal cycle in cloud top temperature from seviri |
| url | http://www.atmos-chem-phys.net/17/7035/2017/acp-17-7035-2017.pdf |
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