Search results for "Earth's energy budget"

The Influence of Trace Substances on the Atmospheric Energy Budget

1979

ABSTRACT The most effective absorbers of solar radiation in the system earth-atmosphere are the earth's surface layer, the atmospheric water vapor, ozone and oxygen. In the troposphere water vapor is dominant, in the lower stratosphere ozone. The absorption contribution due to carbon dioxide may be neglected in both regions of the atmosphere. The contribution of aerosol particles is significant only close to the earth's surface. Here the absorption by aerosol particles equals the effect by water vapor. This fact and the following properties of aerosol particles motivate a special treatment. Particles absorb; particles scatter and elongate the optical path of solar radiation through the abso…

Comparison of aircraft measurements during GoAmazon2014/5 and ACRIDICON-CHUVA

2019

Abstract. The indirect effect of atmospheric aerosol particles on the Earth's radiation balance remains one of the most uncertain components affecting climate change throughout the industrial period. The large uncertainty is partly due to the incomplete understanding of aerosol–cloud interactions. One objective of the GoAmazon2014/5 and the ACRIDICON (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems)-CHUVA (Cloud Processes of the Main Precipitation Systems in Brazil) projects was to understand the influence of emissions from the tropical megacity of Manaus (Brazil) on the surrounding atmospheric environment of the rainforest and to investiga…

Improvements in land surface temperature retrieval from the Landsat series thermal band using water vapor and air temperature

2009

[1] Land surface temperature (LST) is involved in many land surface processes such as evapotranspiration, net radiation, or air temperature modeling. In this paper we present an improved methodology to retrieve LST from Landsat 4 TM, Landsat 5 TM, and Landsat 7 ETM+ using four atmospheric databases covering different water vapor ranges (from 0 to 8 g cm−2) to build the LST retrieval models and using both water vapor and air temperature as input variables. We also compare this with LST retrievals using only water vapor or only air temperature, as well as with an existing LST retrieval algorithm. In order to validate the results, we have selected 77 Landsat images taken between 2002 and 2006 …

Dust emissions over the Sahel associated with the West African monsoon intertropical discontinuity region: A representative case-study

2008

Near-dawn airborne lidar and dropsonde observations acquired on 7 July 2006, during the African Monsoon Multidisciplinary Analysis (AMMA) Special Observing Period 2a1, were used to investigate dust mobilization, lifting and transport in the intertropical discontinuity (ITD) region over western Niger. Atmospheric reflectivity data from the LEANDRE 2 lidar system enabled us to analyse the structure of dust plumes in the context of wind and thermodynamic information provided by the WIND lidar system and dropsondes. Dust mobilization was mainly observed in two locations: (a) within the monsoon flow as the result of the passage of a density current originating from a mesoscale convective system …

ON THE USE OF SATELLITE THERMAL DATA FOR DETERMINING EVAPOTRANSPIRATION IN PARTIALLY VEGETATED AREAS

1992

Abstract The use of satellite data for determining daily evapotranspiration over completely vegetated areas has been analysed by different authors. However, if the soil surface is partially covered by vegetation the problem becomes more complicated, because in this case the value of the temperature measured by the satellite varies with the viewing geometry. In this work we have studied the influence of the satellite observation angle for crops with different cover degree, field geometry and ground emissivity. For this purpose we have used the simplified relation proposed by Jackson et al.LET d=Rnd−B(T3−T a)iwhere ET 4 and R nd are the daily values of evapotranspiration and net radiation res…

The Aqua-Planet Experiment (APE): CONTROL SST Simulation

2013

Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes…

West African Monsoon water cycle: 1. A hybrid water budget data set

2010

International audience; This study investigates the West African Monsoon water cycle with the help of a new hybrid water budget data set developed within the framework of the African Monsoon Multidisciplinary Analyses. Surface water and energy fluxes are estimated from an ensemble of land surface model simulations forced with elaborate precipitation and radiation products derived from satellite observations, while precipitable water tendencies are estimated from numerical weather prediction analyses. Vertically integrated atmospheric moisture flux convergence is estimated as a residual. This approach provides an advanced, comprehensive atmospheric water budget, including evapotranspiration,…

Growth of nucleation mode particles in the summertime Arctic: a case study

2016

Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles,  <  20 nm in diameter, into sizes ab…

2018

Abstract. Mineral dust is an important component of the climate system, affecting the radiation balance, cloud properties, biogeochemical cycles, regional circulation and precipitation, as well as having negative effects on aviation, solar energy generation and human health. Dust size and composition has an impact on all these processes. However, changes in dust size distribution and composition during transport, particularly for coarse particles, are poorly understood and poorly represented in climate models. Here we present new in situ airborne observations of dust in the Saharan Air Layer (SAL) and the marine boundary layer (MBL) at the beginning of its transatlantic transport pathway, f…

Results from the Fourth WMO Filter Radiometer Comparison for aerosol optical depth measurements

2018

Abstract. This study presents the results of the Fourth Filter Radiometer Comparison that was held in Davos, Switzerland, between 28 September and 16 October 2015. Thirty filter radiometers and spectroradiometers from 12 countries participated including reference instruments from global aerosol networks. The absolute differences of all instruments compared to the reference have been based on the World Meteorological Organization (WMO) criterion defined as follows: 95% of the measured data has to be within 0.005 ± 0.001∕m (where m is the air mass). At least 24 out of 29 instruments achieved this goal at both 500 and 865 nm, while 12 out of 17 and 13 out of 21 achieved this at 368 and 412 nm,…