Diurnal variation of upper tropospheric humidity and its relations to convective activities over tropical Africa

Chung, Eunhyea; Sohn, Byung-Ju; Schmetz, Johannes; Koenig, Marianne

doi:10.5194/acp-7-2489-2007

Cited by 45 publications

(66 citation statements)

References 35 publications

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“…The diurnal peak of deep convection in observations occurs nearly at 18 LT and UTH peak time lags the deep convection almost by 8 h. This result is in agreement with Chung et al [42] and Eriksson et al [19]. The late afternoon peak time for the upper tropospheric IWP from SMILES observations has been shown in Millan et al [44].…”

Section: Diurnal Cycle In Models and Observationssupporting

confidence: 81%

“…The diurnal cycle of UTH in observations shown for convective land and oceanic regions are in good agreement in terms of the diurnal maximum and minimum values, with much stronger diurnal amplitudes over land regions in comparison to oceanic regions [19,42]. Chung et al [42] used METEOSAT-8 measurements over A-2 and A-3 to analyze the diurnal cycles of upper and mid-tropospheric humidity in conjunction with the diurnal cycles of clouds and precipitation.…”

Section: Diurnal Cycle In Models and Observationsmentioning

confidence: 99%

“…Chung et al [42] used METEOSAT-8 measurements over A-2 and A-3 to analyze the diurnal cycles of upper and mid-tropospheric humidity in conjunction with the diurnal cycles of clouds and precipitation. Figures 3 and 4 show that the DUR, LTMAX and LTMIN in models differ from that of the microwave observations.…”

Section: Diurnal Cycle In Models and Observationsmentioning

confidence: 99%

See 2 more Smart Citations

Evaluating the Diurnal Cycle of Upper Tropospheric Humidity in Two Different Climate Models Using Satellite Observations

Kottayil

John

Buehler³

et al. 2016

Remote Sensing

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Abstract:The diurnal cycle of upper tropospheric humidity (UTH) is known to be influenced by such processes as convection and the formation of clouds which are parameterized in current global climate models. In this study, we evaluate the performance of two climate models, the Community Atmospheric Model version 5 (CAM-5) and the Global Atmosphere 3.0 (GA-3) model in simulating the diurnal cycle of UTH (represented by a combination of sinusoids of 12 and 24 h periods) by comparing with microwave and infrared (IR) measurements (where available). These comparisons were made over two convective land regions in South America and Africa, and over oceanic regions in the Atlantic, Indian and West Pacific for the month of January 2007. We analyzed how the diurnal cycles from IR and microwave instruments differ, and the reason for the differences. Our study suggests that the differences in the diurnal cycles of IR and microwave UTH result from sampling differences due to the presence of clouds. As noted by earlier studies, the models exhibit considerable discrepancies in diurnal amplitude and phase relative to observations, and these discrepancies have different magnitudes over land and ocean.

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Section: Diurnal Cycle In Models and Observationssupporting

confidence: 81%

Section: Diurnal Cycle In Models and Observationsmentioning

confidence: 99%

See 1 more Smart Citation

Evaluating the Diurnal Cycle of Upper Tropospheric Humidity in Two Different Climate Models Using Satellite Observations

Kottayil

John

Buehler³

et al. 2016

Remote Sensing

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“…Observations of the diurnal variation can be found in many atmospheric variables. Near the ground, weather reports show that surface air temperature, pressure, winds, precipitation (Dai and Deser, 1999; and precipitable water vapor (Dai et al, 2002) vary greatly in 24 h. In the troposphere, satellite radiance measurements reveal a significant diurnal cycle of hydrological processes in terms of precipitation (Nesbitt and Zipser, 2003), deep convection, cloudiness and upper tropospheric humidity (UTH) (e.g., Tian et al, 2004Tian et al, , 2005Chung et al, 2007). From the upper troposphere to the mesosphere and thermosphere, the propagating tidal waves from the water vapor and ozone heating have been extensively investigated and described in the monograph by Chapman and Lindzen (1970).…”

Section: Introductionmentioning

confidence: 99%

Atmospheric diurnal variations observed with GPS radio occultation soundings

Xie

et al. 2010

Atmos. Chem. Phys.

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Abstract. The diurnal variation, driven by solar forcing, is a fundamental mode in the Earth's weather and climate system. Radio occultation (RO) measurements from the six COSMIC satellites (Constellation Observing System for Meteorology, Ionosphere and Climate) provide nearly uniform global coverage with high vertical resolution, all-weather and diurnal sampling capability. This paper analyzes the diurnal variations of temperature and refractivity from three-year (2007)(2008)(2009)) COSMIC RO measurements in the troposphere and stratosphere between 30 • S and 30 • N. The RO observations reveal both propagating and trapped vertical structures of diurnal variations, including transition regions near the tropopause where data with high vertical resolution are critical. In the tropics the diurnal amplitude in refractivity shows the minimum around 14 km and increases to a local maximum around 32 km in the stratosphere. The upward propagating component of the migrating diurnal tides in the tropics is clearly captured by the GPS RO measurements, which show a downward progression in phase from stratopause to the upper troposphere with a vertical wavelength of about 25 km. At ∼32 km the seasonal variation of the tidal amplitude maximizes at the opposite side of the equator relative to the solar forcing. The vertical structure of tidal amplitude shows strong seasonal variations and becomes asymmetric along the equator and tilted toward the summer hemisphere in the solstice months. Such asymmetry becomes less prominent in equinox months.

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“…Most of these studies are based on geostationary infrared (IR) data (e.g. Soden, 2000;Tian et al, 2004;Chung et al, 2007), but also combinations of IR and radar data from the Tropical Rainfall Measuring Mission (Hong et al, 2006;Liu and Zipser, 2008a) as well as IR and passive microwave measurements (Zelinka and Hartmann, 2009) have been used. Typically, IR brightness temperatures at 6.7 µm are used to estimate the clear sky mean relative humidity between 500 and 200 hPa (Soden and Bretherton, 1993), and various thresholds of the 11 µm window channel are used to estimate occurrence frequencies of various cloud types (e.g.…”

Section: Introductionmentioning

confidence: 99%

Diurnal variations of humidity and ice water content in the tropical upper troposphere

et al. 2010

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Abstract.Observational results of diurnal variations of humidity from Odin-SMR and AURA-MLS, and cloud ice mass from Odin-SMR and CloudSat are presented for the first time. Comparisons show that the retrievals of humidity and cloud ice from these two satellite combinations are in good agreement. The retrieved data are combined from four almost evenly distributed times of the day allowing mean values, amplitudes and phases of the diurnal variations around 200 hPa to be estimated. This analysis is applied to six climatologically distinct regions, five located in the tropics and one over the subtropical northern Pacific Ocean. The strongest diurnal cycles are found over tropical land regions, where the amplitude is ∼7% RHi for humidity and ∼50% for ice mass. The greatest ice mass for these regions is found during the afternoon, and the humidity maximum is observed to lag this peak by ∼6 h. Over tropical ocean regions the variations are smaller and the maxima in both ice mass and humidity are found during the early morning. Observed results are compared with output from three climate models (ECHAM, EC-EARTH and CAM3). Direct measurementmodel comparisons were not possible because the measured and modelled cloud ice masses represent different quantities. To make a meaningful comparison, the amount of snow had to be estimated from diagnostic parameters of the models. There is a high probability that the models underestimate the average ice mass (outside the 1-σ uncertainty). The models also show clear deficiencies when it comes to amplitude and phase of the regional variations, but to varying degrees.

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Diurnal variation of upper tropospheric humidity and its relations to convective activities over tropical Africa

Cited by 45 publications

References 35 publications

Evaluating the Diurnal Cycle of Upper Tropospheric Humidity in Two Different Climate Models Using Satellite Observations

Evaluating the Diurnal Cycle of Upper Tropospheric Humidity in Two Different Climate Models Using Satellite Observations

Atmospheric diurnal variations observed with GPS radio occultation soundings

Diurnal variations of humidity and ice water content in the tropical upper troposphere

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