A critical look at spatial scale choices in satellite-based aerosol indirect effect studies
Analysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships be...
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Copernicus Publications
2010-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/10/11459/2010/acp-10-11459-2010.pdf |
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doaj-3501bfdeabd04cdd971656b0c78f5d552020-11-24T22:55:04ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242010-12-011023114591147010.5194/acp-10-11459-2010A critical look at spatial scale choices in satellite-based aerosol indirect effect studiesB. S. Grandey0P. Stier1Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UKAtmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UKAnalysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships between aerosol optical depth τ<sub>a</sub> derived liquid cloud droplet effective number concentration <i>N</i><sub>e</sub> and liquid cloud droplet effective radius <i>r</i><sub>e</sub> at different spatial scales. Generally, positive values of <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: 10px; color: #000;">dln<i>N</i><sub>e</sub></span><span style="margin-left: -3em; margin-right: .5em; vertical-align: -15%; font-size: 10px; color: #000;">dlnτ<sub>a</sub></span> are found for ocean regions, whilst negative values occur for many land regions. The spatial distribution of <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: 10px; color: #000;">dln<i>r</i><sub>e</sub></span><span style="margin-left: -2.7em; margin-right: .5em; vertical-align: -15%; font-size: 10px; color: #000;">dlnτ<sub>a</sub></span> shows approximately the opposite pattern, with generally postive values for land regions and negative values for ocean regions. We find that for region sizes larger than 4° × 4°, spurious spatial variations in retrieved cloud and aerosol properties can introduce widespread significant errors to calculations of <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: 10px; color: #000;">dln<i>N</i><sub>e</sub></span><span style="margin-left: -3em; margin-right: .5em; vertical-align: -15%; font-size: 10px; color: #000;">dlnτ<sub>a</sub></span> and <span style="border-bottom: 1px solid #000; vertical-align: 50%; font-size: 10px; color: #000;">dln<i>r</i><sub>e</sub></span><span style="margin-left: -2.7em; margin-right: .5em; vertical-align: -15%; font-size: 10px; color: #000;">dlnτ<sub>a</sub></span>. For regions on the scale of 60° × 60°, these methodological errors may lead to an overestimate in global cloud albedo effect radiative forcing of order 80% relative to that calculated for regions on the scale of 1° × 1°.http://www.atmos-chem-phys.net/10/11459/2010/acp-10-11459-2010.pdf |
| collection |
DOAJ |
| language |
English |
| format |
Article |
| sources |
DOAJ |
| author |
B. S. Grandey P. Stier |
| spellingShingle |
B. S. Grandey P. Stier A critical look at spatial scale choices in satellite-based aerosol indirect effect studies Atmospheric Chemistry and Physics |
| author_facet |
B. S. Grandey P. Stier |
| author_sort |
B. S. Grandey |
| title |
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| title_short |
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| title_full |
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| title_fullStr |
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| title_full_unstemmed |
A critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| title_sort |
critical look at spatial scale choices in satellite-based aerosol indirect effect studies |
| publisher |
Copernicus Publications |
| series |
Atmospheric Chemistry and Physics |
| issn |
1680-7316 1680-7324 |
| publishDate |
2010-12-01 |
| description |
Analysing satellite datasets over large regions may introduce spurious
relationships between aerosol and cloud properties due to spatial variations
in aerosol type, cloud regime and synoptic regime climatologies. Using
MODerate resolution Imaging Spectroradiometer data, we calculate
relationships between aerosol optical depth τ<sub>a</sub> derived liquid
cloud droplet effective number concentration <i>N</i><sub>e</sub> and liquid cloud
droplet effective radius <i>r</i><sub>e</sub> at different spatial scales. Generally,
positive values of <span style="border-bottom: 1px solid #000; vertical-align: 50%;
font-size: 10px; color: #000;">dln<i>N</i><sub>e</sub></span><span style="margin-left: -3em;
margin-right: .5em; vertical-align: -15%; font-size: 10px; color:
#000;">dlnτ<sub>a</sub></span> are found for ocean regions, whilst negative values occur for many land
regions. The spatial distribution of <span style="border-bottom: 1px solid #000; vertical-align: 50%;
font-size: 10px; color: #000;">dln<i>r</i><sub>e</sub></span><span style="margin-left: -2.7em;
margin-right: .5em; vertical-align: -15%; font-size: 10px; color:
#000;">dlnτ<sub>a</sub></span> shows approximately the opposite pattern, with
generally postive values for land regions and negative values for ocean
regions. We find that for region sizes larger than
4° × 4°, spurious spatial variations in retrieved
cloud and aerosol properties can introduce widespread significant errors to
calculations of <span style="border-bottom: 1px solid #000; vertical-align: 50%;
font-size: 10px; color: #000;">dln<i>N</i><sub>e</sub></span><span style="margin-left: -3em;
margin-right: .5em; vertical-align: -15%; font-size: 10px; color:
#000;">dlnτ<sub>a</sub></span> and <span style="border-bottom: 1px solid #000; vertical-align: 50%;
font-size: 10px; color: #000;">dln<i>r</i><sub>e</sub></span><span style="margin-left: -2.7em;
margin-right: .5em; vertical-align: -15%; font-size: 10px; color:
#000;">dlnτ<sub>a</sub></span>. For regions on the
scale of 60° × 60°, these methodological errors may
lead to an overestimate in global cloud albedo effect radiative forcing of
order 80% relative to that calculated for regions on the scale of 1° × 1°. |
| url |
http://www.atmos-chem-phys.net/10/11459/2010/acp-10-11459-2010.pdf |
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