Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans
Differences in cloud droplet effective radius and cloud droplet number concentration (CDNC) estimates inferred from the Aqua–MODIS (Moderate Resolution Imaging Spectroradiometer) collections 5.1 (C5.1) and 6 (C6) cloud products (MYD06) are examined for warm clouds over global oceans for the year...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/10/2105/2017/amt-10-2105-2017.pdf |
| _version_ | 1818977567445614592 |
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| author | J. Rausch K. Meyer R. Bennartz R. Bennartz S. Platnick |
| author_facet | J. Rausch K. Meyer R. Bennartz R. Bennartz S. Platnick |
| author_sort | J. Rausch |
| collection | DOAJ |
| description | Differences in cloud droplet effective radius and cloud droplet
number concentration (CDNC) estimates inferred from the Aqua–MODIS (Moderate Resolution Imaging
Spectroradiometer)
collections 5.1 (C5.1) and 6 (C6) cloud products (MYD06) are examined for warm clouds
over global oceans for the year 2008. Individual pixel level retrievals for
both collections are aggregated to 1° × 1° and
compared globally and regionally for the three main spectral channel pairs
used for MODIS cloud optical property retrievals. Comparisons between both
collections are performed for cases in which all three effective radii
retrievals are classified by the MODIS cloud product as valid. The
contribution to the observed differences of several key MYD06 Collection 6
algorithm updates are also explored, with a focus on changes to the surface
reflectance model, assumed solar irradiance, above-cloud emission, cloud-top
pressure (CTP), and pixel registration. Global results show a neutral to positive
(> 50 cm<sup>−3</sup>) change for C6-derived CDNC relative to C5.1 for
the 1.6 and 2.1 µm channel retrievals, corresponding to a
neutral to −2 µm difference in droplet effective radius (<i>r</i><sub>e</sub>). For 3.7 µm
retrievals, CDNC results show a negative change in the tropics, with
differences transitioning toward positive values with increasing latitude
spanning −25 to +50 cm<sup>−3</sup> related to a +2.5 to −1 µm transition
in effective radius. Cloud optical thickness (<i>τ</i>) differences were small relative
to effective radius and found to not significantly impact CDNC estimates.
Regionally, the magnitude and behavior of the annual CDNC cycle are compared
for each effective radius retrieval. Results from this study indicate
significant inter-collection differences in aggregated values of effective
radius due to changes to the precomputed retrieval lookup tables (LUTs) for ocean
scenes, changes to retrieved cloud-top pressure, solar irradiance, or above-cloud thermal emission, depending upon spectral channel. The observed
differences between collections may have implications for existing MODIS-derived climatologies and validation studies of effective radius and CDNC. |
| first_indexed | 2024-12-20T16:29:48Z |
| format | Article |
| id | doaj.art-d38542802071433ca47c297c4f5728d8 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-20T16:29:48Z |
| publishDate | 2017-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-d38542802071433ca47c297c4f5728d82022-12-21T19:33:18ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482017-06-01102105211610.5194/amt-10-2105-2017Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceansJ. Rausch0K. Meyer1R. Bennartz2R. Bennartz3S. Platnick4Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37235, USANASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USADepartment of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37235, USASpace Science and Engineering Center, University of Wisconsin, Madison, Madison, WI 53706, USA NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USADifferences in cloud droplet effective radius and cloud droplet number concentration (CDNC) estimates inferred from the Aqua–MODIS (Moderate Resolution Imaging Spectroradiometer) collections 5.1 (C5.1) and 6 (C6) cloud products (MYD06) are examined for warm clouds over global oceans for the year 2008. Individual pixel level retrievals for both collections are aggregated to 1° × 1° and compared globally and regionally for the three main spectral channel pairs used for MODIS cloud optical property retrievals. Comparisons between both collections are performed for cases in which all three effective radii retrievals are classified by the MODIS cloud product as valid. The contribution to the observed differences of several key MYD06 Collection 6 algorithm updates are also explored, with a focus on changes to the surface reflectance model, assumed solar irradiance, above-cloud emission, cloud-top pressure (CTP), and pixel registration. Global results show a neutral to positive (> 50 cm<sup>−3</sup>) change for C6-derived CDNC relative to C5.1 for the 1.6 and 2.1 µm channel retrievals, corresponding to a neutral to −2 µm difference in droplet effective radius (<i>r</i><sub>e</sub>). For 3.7 µm retrievals, CDNC results show a negative change in the tropics, with differences transitioning toward positive values with increasing latitude spanning −25 to +50 cm<sup>−3</sup> related to a +2.5 to −1 µm transition in effective radius. Cloud optical thickness (<i>τ</i>) differences were small relative to effective radius and found to not significantly impact CDNC estimates. Regionally, the magnitude and behavior of the annual CDNC cycle are compared for each effective radius retrieval. Results from this study indicate significant inter-collection differences in aggregated values of effective radius due to changes to the precomputed retrieval lookup tables (LUTs) for ocean scenes, changes to retrieved cloud-top pressure, solar irradiance, or above-cloud thermal emission, depending upon spectral channel. The observed differences between collections may have implications for existing MODIS-derived climatologies and validation studies of effective radius and CDNC.http://www.atmos-meas-tech.net/10/2105/2017/amt-10-2105-2017.pdf |
| spellingShingle | J. Rausch K. Meyer R. Bennartz R. Bennartz S. Platnick Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans Atmospheric Measurement Techniques |
| title | Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans |
| title_full | Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans |
| title_fullStr | Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans |
| title_full_unstemmed | Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans |
| title_short | Differences in liquid cloud droplet effective radius and number concentration estimates between MODIS collections 5.1 and 6 over global oceans |
| title_sort | differences in liquid cloud droplet effective radius and number concentration estimates between modis collections 5 1 and 6 over global oceans |
| url | http://www.atmos-meas-tech.net/10/2105/2017/amt-10-2105-2017.pdf |
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