Discriminating raining from non-raining clouds at mid-latitudes using multispectral satellite data

Abstract. We propose a new method for the delineation of precipitation using cloud properties derived from optical satellite data. This approach is not only sufficient for the detection of mainly convective precipitation by means of the commonly used connection between infrared cloud top temperature and rainfall probability but enables the detection of stratiform precipitation (e.g., in connection with mid-latitude frontal systems). The scheme presented is based on the concept model, that precipitating clouds must have both a sufficient vertical extent and large enough droplets. Therefore, we have analysed MODIS scenes during the severe European summer floods in 2002 and retrieved functions for the computation of an auto-adaptive threshold value of the effective cloud droplet radius with respect to the corresponding optical thickness which links these cloud properties with rainfall areas on a pixel basis.

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Discriminating raining from non-raining clouds at mid-latitudes using multispectral satellite data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-1385-2006 ◽

2006 ◽

Vol 6 (1) ◽

pp. 1385-1398 ◽

Cited By ~ 3

Author(s):

T. Nauss ◽

A. A. Kokhanovsky

Keyword(s):

Satellite Data ◽

Cloud Droplet ◽

Threshold Value ◽

Droplet Radius ◽

Concept Model ◽

Cloud Properties ◽

Frontal Systems ◽

Terra Modis ◽

Precipitating Clouds ◽

Cloud Top Temperature

Abstract. We propose a new method for the delineation of precipitation using cloud properties derived from optical satellite data. This approach is not only sufficient for the detection of mainly convective driven precipitation by means of the commonly used connection between infrared cloud-top temperature and rainfall probability but enables the detection of stratiform precipitation (e.g., in connection with mid-latitude frontal systems). The scheme presented is based on the concept model, that precipitating clouds must have both a large enough vertical extent and large enough droplets. Therefore, we have analyzed Terra-MODIS scenes during the severe European summer floods in 2002 and retrieved functions for the computation of an auto-adaptive threshold value of the effective cloud droplet radius with respect to the corresponding optical thickness which links these cloud properties with rainfall areas on a pixel basis.

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Discriminating raining from non-raining clouds at mid-latitudes using meteosat second generation daytime data

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-2341-2008 ◽

2008 ◽

Vol 8 (9) ◽

pp. 2341-2349 ◽

Cited By ~ 34

Author(s):

B. Thies ◽

T. Nauss ◽

J. Bendix

Keyword(s):

Cloud Water ◽

Convective Precipitation ◽

Rain Area ◽

Water Path ◽

Vertical Extension ◽

Frontal Systems ◽

Cloud Water Path ◽

Precipitating Clouds ◽

Cloud Top Temperature ◽

Supply Information

Abstract. A new method for the delineation of precipitation during daytime using multispectral satellite data is proposed. The approach is not only applicable to the detection of mainly convective precipitation by means of the commonly used relation between infrared cloud top temperature and rainfall probability but enables also the detection of stratiform precipitation (e.g. in connection with mid-latitude frontal systems). The presented scheme is based on the conceptual model that precipitating clouds are characterized by a combination of particles large enough to fall, an adequate vertical extension (both represented by the cloud water path; cwp), and the existence of ice particles in the upper part of the cloud. The technique considers the VIS0.6 and the NIR1.6 channel to gain information about the cloud water path. Additionally, the brightness temperature differences ΔT8.7-10.8 and ΔT10.8-12.1 are considered to supply information about the cloud phase. Rain area delineation is realized by using a minimum threshold of the rainfall confidence. To obtain a statistical transfer function between the rainfall confidence and the four parameters VIS

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Assignment of rainfall confidence values using multispectral satellite data at mid-latitudes: first results

Advances in Geosciences ◽

10.5194/adgeo-10-99-2007 ◽

2007 ◽

Vol 10 ◽

pp. 99-102 ◽

Cited By ~ 22

Author(s):

T. Nauss ◽

A. A. Kokhanovsky

Keyword(s):

Satellite Data ◽

Liquid Water ◽

Regression Function ◽

Radar Data ◽

New Method ◽

Droplet Radius ◽

Liquid Water Path ◽

Water Path ◽

Concept Model ◽

Cloud Properties

Abstract. The authors propose a new method for the assignment of rainfall confidences on a pixel basis using cloud properties derived from optical satellite data during daytime. This approach is based on the concept model that the probability for precipitation is a function of the liquid water path, which in turn can be computed using the satellite-retrieved cloud optical thickness and the cloud effective droplet radius. In order to evaluate the principal potential of this idea, scenes from the Terra-MODIS sensor during the severe European summer floods in 2002 have been analysed in order to derive a corresponding regression function that interlinks the liquid water path with the rainfall probability or better with the confidence that a pixel which is classified as raining does actually rain. A first evaluation against ground-based radar data during March 2004 shows good skill of this new method.

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The impact of sampling strategy on the cloud droplet number concentration estimated from satellite data

10.5194/amt-2021-371 ◽

2021 ◽

Author(s):

Edward Gryspeerdt ◽

Daniel T. McCoy ◽

Ewan Crosbie ◽

Richard H. Moore ◽

Graeme J. Nott ◽

...

Keyword(s):

Satellite Data ◽

Radiative Forcing ◽

Sampling Strategy ◽

Cloud Droplet ◽

Number Concentration ◽

Cloud Properties ◽

Systematic Biases ◽

Cloud Droplet Number Concentration ◽

Aerosol Cloud Interactions ◽

The Impact

Abstract. Cloud droplet number concentration (Nd) is of central importance to observation-based estimates of aerosol indirect effects, being used to quantify both the cloud sensitivity to aerosol and the base state of the cloud. However, the derivation of Nd from satellite data depends on a number of assumptions about the cloud and the accuracy of the retrievals of the cloud properties from which it is derived, making it prone to systematic biases. A number of sampling strategies have been proposed to address these biases by selecting the most accurate Nd retrievals in the satellite data. This work compares the impact of these strategies on the accuracy of the satellite retrieved Nd, using a selection of insitu measurements. In stratocumulus regions, the MODIS Nd retrieval is able to achieve a high precision (r2 of 0.5–0.8). This is lower in other cloud regimes, but can be increased by appropriate sampling choices. Although the Nd sampling can have significant effects on the Nd climatology, it produces only a 20 % variation in the implied radiative forcing from aerosol-cloud interactions, with the choice of aerosol proxy driving the overall uncertainty. The results are summarised into recommendations for using MODIS Nd products and appropriate sampling.

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Discriminating raining from non-raining clouds at mid-latitudes using Meteosat Second Generation daytime data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-15853-2007 ◽

2007 ◽

Vol 7 (6) ◽

pp. 15853-15872 ◽

Cited By ~ 1

Author(s):

B. Thies ◽

T. Nauss ◽

J. Bendix

Keyword(s):

Transfer Function ◽

Radar Data ◽

Cloud Water ◽

Convective Precipitation ◽

Rain Area ◽

Water Path ◽

Vertical Extension ◽

Cloud Water Path ◽

Precipitating Clouds ◽

Cloud Top Temperature

Abstract. A new method for the delineation of precipitation during daytime using multispectral satellite data is proposed. The approach is not only applicable to the detection of mainly convective precipitation by means of the commonly used relation between infrared cloud top temperature and rainfall probability but enables also the detection of stratiform precipitation (e.g. in connection with mid-latitude frontal systems). The presented scheme is based on the conceptual model that precipitating clouds are characterized by a combination of particles large enough to fall, an adequate vertical extension (both represented by the cloud water path (cwp)), and the existence of ice particles in the upper part of the cloud. The technique considers the VIS0.6 and the NIR1.6 channel to gain information about the cloud water path. Additionally, the channel differences ΔT8.7-10.8 and ΔT10.8-12.1 are considered to supply information about the cloud phase. Rain area delineation is realized by using a minimum threshold of the rainfall confidence. To obtain a statistical transfer function between the rainfall confidence and the channel differences, the value combination of the four variables is compared to ground based radar data. The retrieval is validated against independent radar data not used for deriving the transfer function and shows an encouraging performance as well as clear improvements compared to existing optical retrieval techniques using only IR thresholds for cloud top temperature.

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Conditions for super-adiabatic droplet growth after entrainment mixing

10.5194/acp-2016-94 ◽

2016 ◽

Author(s):

Fan Yang ◽

Raymond Shaw ◽

Huiwen Xue

Keyword(s):

Cloud Model ◽

Cloud Droplet ◽

Droplet Radius ◽

Droplet Growth ◽

Critical Height ◽

Growth Region ◽

Cloud Droplets ◽

Cloud Properties ◽

Environment Temperature ◽

Environmental Air

Abstract. Cloud droplet response to entrainment and mixing between a cloud and its environment is often considered by itself, without accounting for subsequent growth after the mixing event. Here we consider the change in cloud properties when the mixed parcel rises adiabatically after the mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction due to mixing to be predicted from the mixing fraction and the cloud and environment temperature and humidity. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: At the critical height the cloud droplet radius is the same for both mixed and unmixed parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the "super-adiabatic" growth region. Analytical results are confirmed by a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixing parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius under polydisperse conditions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision-coalescence in warm clouds.

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Contrasting Influences of Recent Aerosol Changes on Clouds and Precipitation in Europe and East Asia

Journal of Climate ◽

10.1175/jcli-d-14-00837.1 ◽

2015 ◽

Vol 28 (22) ◽

pp. 8770-8790 ◽

Cited By ~ 3

Author(s):

Camilla W. Stjern ◽

Jón Egill Kristjánsson

Keyword(s):

East Asia ◽

Droplet Size ◽

Liquid Water ◽

Cloud Droplet ◽

Convective Precipitation ◽

Release Mechanism ◽

Aerosol Forcing ◽

Cloud Properties ◽

Simulated Precipitation ◽

Aerosol Cloud Interactions

Abstract Over the last few decades, aerosol loadings have increased greatly over Southeast Asia, while Europe and North America have experienced huge reductions. Previous studies have suggested that these changes may have influenced the temperature trends as well as precipitation patterns due to the direct and semidirect aerosol effects. Here, an Earth system model with parameterized aerosol–radiation and aerosol–cloud interactions is used to investigate changes in cloud properties and precipitation between 1975 and 2005. This is done globally as well as for the two focus areas Europe and East Asia. Despite systematic changes in cloud droplet number concentration and cloud droplet size, changes in stratiform precipitation are less clear. In both regions there is a dominance of autoconversion over liquid water accretion as the primary precipitation release mechanism, which alone should imply a strong sensitivity to changes in cloud droplet size. However, in these areas liquid water paths are relatively low and background concentrations are high, which produce low simulated precipitation susceptibilities. High susceptibilities are instead found over remote ocean regions, in agreement with expectations. For convective precipitation, both regions show statistically significant changes that are consistent with oppositely signed changes in direct aerosol forcing over Europe and East Asia, respectively.

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Estimates of Aerosol Indirect Effect from Terra MODIS over Republic of Korea

Advances in Meteorology ◽

10.1155/2013/976813 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 7

Author(s):

Woon-Seon Jung ◽

A. S. Panicker ◽

Dong-In Lee ◽

Sung-Hwa Park

Keyword(s):

Indirect Effect ◽

Yellow Sea ◽

Cloud Droplet ◽

Cloud Water ◽

Republic Of Korea ◽

Droplet Radius ◽

Monsoon Period ◽

Aerosol Indirect Effect ◽

Cloud Properties ◽

Cloud Ice

Moderate resolution imaging spectroradiometer (MODIS) data have been analyzed over four different regions (Yellow sea, Korean inland, East Sea, and South Sea) in Republic of Korea to investigate the seasonal variability of aerosol-cloud properties and aerosol indirect effect during the past decade (2000–2009). Aerosol optical depth (AOD) was found to be consistently high during spring. Cloud ice radius (CIR) also showed higher values during spring, while an enhancement in cloud water radius (CWR) and fine mode fraction (FMF) was observed during summer. AOD and aerosol index (AI) were found to be higher during January to June. However, FMF and CWR showed enhancement during July to December. Aerosol indirect effect (AIE) in each year has been estimated and found to be showing positive and negative indirect effects. The AIE for fixed cloud ice path (CIP) showed positive indirect effect (Twomey effect) over Yellow sea, while the AIE for fixed cloud water path (CWP) showed a major negative indirect effect (anti-Twomey effect) over all regions. During Changma (summer monsoon) period, the AIE for both CIP and CWP showed dominant anti-Twomey effect in middle and low level clouds, indicating the growth of cloud droplet radius with changes in aerosols, enhancing the precipitation.

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Modeling microphysical effects of entrainment in clouds observed during EUCAARI-IMPACT field campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-8489-2013 ◽

2013 ◽

Vol 13 (16) ◽

pp. 8489-8503 ◽

Cited By ~ 2

Author(s):

D. Jarecka ◽

H. Pawlowska ◽

W. W. Grabowski ◽

A. A. Wyszogrodzki

Keyword(s):

Boundary Layer ◽

Turbulent Mixing ◽

Marine Boundary Layer ◽

Cloud Droplet ◽

Droplet Radius ◽

Subgrid Scale ◽

Microphysics Scheme ◽

Local Conditions ◽

Field Campaign ◽

Les Model

Abstract. This paper discusses aircraft observations and large-eddy simulation (LES) modeling of 15 May 2008, North Sea boundary-layer clouds from the EUCAARI-IMPACT field campaign. These clouds are advected from the northeast by the prevailing lower-tropospheric winds and featured stratocumulus-over-cumulus cloud formations. An almost-solid stratocumulus deck in the upper part of the relatively deep, weakly decoupled marine boundary layer overlays a field of small cumuli. The two cloud formations have distinct microphysical characteristics that are in general agreement with numerous past observations of strongly diluted shallow cumuli on one hand and solid marine stratocumulus on the other. Based on the available observations, a LES model setup is developed and applied in simulations using a novel LES model. The model features a double-moment warm-rain bulk microphysics scheme combined with a sophisticated subgrid-scale scheme allowing local prediction of the homogeneity of the subgrid-scale turbulent mixing. The homogeneity depends on the characteristic time scales for the droplet evaporation and for the turbulent homogenization. In the model, these scales are derived locally based on the subgrid-scale turbulent kinetic energy, spatial scale of cloudy filaments, mean cloud droplet radius, and humidity of the cloud-free air entrained into a cloud, all predicted by the LES model. The model reproduces contrasting macrophysical and microphysical characteristics of the cumulus and stratocumulus cloud layers. Simulated subgrid-scale turbulent mixing within the cumulus layer and near the stratocumulus top is on average quite inhomogeneous, but varies significantly depending on the local conditions.

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