Direct Radiative Effect of Mineral Dust on the Middle East and North Africa Climate

Handle URI:
http://hdl.handle.net/10754/621965
Title:
Direct Radiative Effect of Mineral Dust on the Middle East and North Africa Climate
Authors:
Bangalath, Hamza Kunhu ( 0000-0003-1844-8236 )
Abstract:
Dust-climate interaction over the Middle East and North Africa (MENA) has long been studied, as it is the "dustiest" region on earth. However, the quantitative and qualitative understanding of the role of dust direct radiative effect on MENA climate is still rudimentary. The present dissertation investigates dust direct radiative effect on MENA climate during summer with a special emphasis on the sensitivity of climate response to dust shortwave absorption, which is one of the most uncertain components of dust direct radiative effect. Simulations are conducted with and without dust radiative effect, to differentiate the effect of dust on climate. To elucidate the sensitivity of climate response to dust shortwave absorption, simulations with dust assume three different cases of dust shortwave absorption, representing dust as a very efficient, standard and inefficient shortwave absorber. The non-uniformly distributed dust perturb circulations at various scales. Therefore, the present study takes advantage of the high spatial resolution capabilities of an Atmospheric General Circulation Model (AGCM), High Resolution Atmospheric Model (HiRAM), which incorporates global and regional circulations. AMIP-style global high-resolution simulations are conducted at a spatial resolution of 25 km. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Similarly, the temperature under rainbelt cools and that over subtropical deserts warms. Inter-comparison of various dust shortwave absorption cases shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases in response to dust radiative effect. The maximum response and sensitivity are predicted over this region. The sensitivity of the responses over Sahel, especially that of precipitation, is comparable to the mean state. Locally, the precipitation increase reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. As the region is characterized by the "Sahel drought", the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. The present study, therefore, suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the MENA climate in general, and of Sahel in particular.
Advisors:
Stenchikov, Georgiy L. ( 0000-0001-9033-4925 )
Committee Member:
Jones, Burton ( 0000-0002-9599-1593 ) ; McCabe, Matthew ( 0000-0002-1279-5272 ) ; Lelieveld, Johannes
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Earth Sciences and Engineering
Issue Date:
Nov-2016
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorStenchikov, Georgiy L.en
dc.contributor.authorBangalath, Hamza Kunhuen
dc.date.accessioned2016-12-07T13:37:34Z-
dc.date.available2016-12-07T13:37:34Z-
dc.date.issued2016-11-
dc.identifier.urihttp://hdl.handle.net/10754/621965-
dc.description.abstractDust-climate interaction over the Middle East and North Africa (MENA) has long been studied, as it is the "dustiest" region on earth. However, the quantitative and qualitative understanding of the role of dust direct radiative effect on MENA climate is still rudimentary. The present dissertation investigates dust direct radiative effect on MENA climate during summer with a special emphasis on the sensitivity of climate response to dust shortwave absorption, which is one of the most uncertain components of dust direct radiative effect. Simulations are conducted with and without dust radiative effect, to differentiate the effect of dust on climate. To elucidate the sensitivity of climate response to dust shortwave absorption, simulations with dust assume three different cases of dust shortwave absorption, representing dust as a very efficient, standard and inefficient shortwave absorber. The non-uniformly distributed dust perturb circulations at various scales. Therefore, the present study takes advantage of the high spatial resolution capabilities of an Atmospheric General Circulation Model (AGCM), High Resolution Atmospheric Model (HiRAM), which incorporates global and regional circulations. AMIP-style global high-resolution simulations are conducted at a spatial resolution of 25 km. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Similarly, the temperature under rainbelt cools and that over subtropical deserts warms. Inter-comparison of various dust shortwave absorption cases shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases in response to dust radiative effect. The maximum response and sensitivity are predicted over this region. The sensitivity of the responses over Sahel, especially that of precipitation, is comparable to the mean state. Locally, the precipitation increase reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. As the region is characterized by the "Sahel drought", the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. The present study, therefore, suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the MENA climate in general, and of Sahel in particular.en
dc.language.isoenen
dc.subjectDust Radiative Forcingen
dc.subjectDust Shortwave Absorptionen
dc.subjectMiddle East and North Africaen
dc.subjectHigh Resolution Atmospheric Modelen
dc.subjectSahel Rainfallen
dc.subjectLocal Hadley Circulationen
dc.titleDirect Radiative Effect of Mineral Dust on the Middle East and North Africa Climateen
dc.typeDissertationen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberJones, Burtonen
dc.contributor.committeememberMcCabe, Matthewen
dc.contributor.committeememberLelieveld, Johannesen
thesis.degree.disciplineEarth Sciences and Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id113339en
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