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

Kottayil, Ajil; John, Viju O.; Buehler, Stefan A.; Mohanakumar, K.

doi:10.3390/rs8040325

Cited by 14 publications

(7 citation statements)

References 48 publications

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“…5c, 6c). The peak time of RH "release" from the cloud oscillates between late afternoon and early morning maxima (Kottayil et al, 2016) and its lag with respect to cirrus can be estimated as ∼ 3.5 h. Finally, thin cirrus show good coupling with high opaque clouds and the cirrus, and the amplitudes of their diurnal cycle are comparable with those of the cirrus. The peak times for these clouds have broad distributions that make it difficult to estimate the lags.…”

Section: Variablementioning

confidence: 88%

Diurnal variation of high-level clouds from the synergy of AIRS and IASI space-borne infrared sounders

Stubenrauch

2019

Atmos. Chem. Phys.

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Abstract. By covering about 30 % of the Earth and by exerting a strong greenhouse effect, high-level clouds play an important role in the energy balance of our planet. Their warming and cooling effects within the atmosphere strongly depend on their emissivity. The combination of cloud data from two space-borne infrared sounders, the Atmospheric InfraRed Sounder, AIRS, and the Infrared Atmospheric Sounding Interferometer, IASI, which observe the Earth four times per day, allows us to investigate the diurnal variation of these high-level clouds by distinguishing between high opaque, cirrus, and thin cirrus clouds. We demonstrate that the diurnal phase and amplitude of high-level clouds can be estimated from these measurements with an uncertainty of 1.5 h and 20 %, respectively. By applying the developed methodology to AIRS and IASI cloud observations for the period of 2008–2015, we obtained monthly geographical distributions of diurnal phase and amplitude at a spatial resolution of 1∘ latitude ×1∘ longitude. In agreement with other studies, the diurnal cycle of high-level clouds is the largest over land in the tropics. At higher latitudes, their diurnal cycle is the largest during the summer. For selected continental regions we found diurnal amplitudes of cloud amount of about 7 % for high opaque clouds and for thin cirrus, and 9 % for cirrus. Over ocean, these values are 2 to 3 times smaller. The diurnal cycle of tropical thin cirrus seems to be similar over land and over ocean, with a minimum in the morning (09:00 LT) and a maximum during the night (01:00 LT). Tropical high opaque clouds have a maximum in the evening (21:00 LT over land), a few hours after the peak of convective rain. This lag can be explained by the fact that this cloud type includes not only the convective cores, but also part of the thicker anvils. Tropical cirrus show maximum coverage during the night (01:00 LT over land). This lag indicates that they are part of the deep convective cloud systems. However, the peak local times also vary regionally. We are providing a global monthly database of detected diurnal cycle amplitude and phase for each of these three high-level cloud types.

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Section: Variablementioning

confidence: 88%

Diurnal variation of high-level clouds from the synergy of AIRS and IASI space-borne infrared sounders

Stubenrauch

2019

Atmos. Chem. Phys.

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“…Hence, while the diurnal variations of the total precipitable water and cloud amounts across the tropics have been established (e.g. 11–13 ), most of the satellite-based studies 14–19 and most model studies 4,10,20–24 do not include the detailed vertical dimension necessary to robustly distinguish the diurnal cycles of humidity 25–28 and clouds in the lower troposphere and the free troposphere. Furthermore, satellite-based climatologies are usually less robust over land than ocean, which limits the possibility to contrast the diurnal cycle of clouds and water vapor over the different surfaces.…”

Section: Introductionmentioning

confidence: 99%

Diurnal variations of cloud and relative humidity profiles across the tropics

Chepfer

Brogniez

Noël

2019

Sci Rep

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Even though the diurnal cycle of solar forcing on the climate system is well defined, the diurnal evolutions of water vapor and clouds induced by the solar forcing are not yet established across the tropics. Here we combine recent satellite observations of clouds profiles and relative humidity profiles to document the diurnal variations of the water vapor and clouds vertical distributions over all the tropics in June-July-August. While the daily mean water vapor and cloud profiles are different between land and ocean, their diurnal variations with respect to their daily means exhibit similar features. Relative humidity profiles and optically thin cloud fraction profiles vary together which maximize during night-time in the entire troposphere and a minimize in day-time. The fraction of optically opaque clouds peak in the free troposphere in the early afternoon, transforms into a high altitude positive anomaly of optically thin clouds from nightfall to sunrise. In addition, land regions exhibit a daily low thin cloud positive anomaly, while oceanic regions exposed to subsidence air motions exhibit positive anomalies of opaque clouds in the lower atmosphere during the second half of the night, which grow until sunrise.

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“…A third key assumption is that the diurnal cycle is small compared to the natural variability (which is fulfilled given the small amplitude of the diurnal cycle for sounding channels reported in other studies; Kottayil et al, , ; Chung et al, ; Chung, Soden, Sohn, et al, ) and that in consequence the distribution of the variability inside the 0.8 K SEVIRI matchup thresholds is unbiased. We tested this by examining the SEVIRI brightness temperature difference between the two microwave matchup pair members (not shown), and it is indeed uniform between −0.8 and +0.8 K, with the exception of a modest spike at zero due to SEVIRI numeric truncation noise, which has no impact on the results.…”

Section: Discussionmentioning

confidence: 97%

Opportunistic Constant Target Matching—A New Method for Satellite Intercalibration

Buehler

Prange

Mrziglod

et al. 2020

Earth and Space Science

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Opportunistic constant target matching is a new method for satellite intercalibration. It solves a long-standing issue with the traditional simultaneous nadir overpass (SNO) method, namely, that it typically provides only data points with cold brightness temperatures for humidity sounding instruments on sun-synchronous satellites. In the new method, a geostationary infrared sensor (SEVIRI) is used to select constant target matches for two different microwave sensors (MHS on NOAA 18 and Metop A). We discuss the main assumptions and limitations of the method and explore its statistical properties with a simple Monte Carlo simulation. The method was tested in a simple case study with real observations for this combination of satellites for MHS Channel 3 at 183 ± 1 GHz, the upper tropospheric humidity channel. For the studied 3-month test period, real observations are found to behave consistently with the simulations, increasing our confidence that the method can be a valuable tool for intercalibration efforts. For the selected case study, the new method confirms that the bias between NOAA 18 and Metop A MHS Channel 3 is very small, with absolute value below 0.05 K.

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

Cited by 14 publications

References 48 publications

Diurnal variation of high-level clouds from the synergy of AIRS and IASI space-borne infrared sounders

Diurnal variation of high-level clouds from the synergy of AIRS and IASI space-borne infrared sounders

Diurnal variations of cloud and relative humidity profiles across the tropics

Opportunistic Constant Target Matching—A New Method for Satellite Intercalibration

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