scholarly journals Evaluation of Modeled Stratocumulus-Capped Boundary Layer Turbulence with Shipborne Data

2013 ◽  
Vol 70 (12) ◽  
pp. 3895-3919 ◽  
Author(s):  
Takanobu Yamaguchi ◽  
W. Alan Brewer ◽  
Graham Feingold
Keyword(s):  
Stationary State ◽  
Domain Size ◽  
Horizontal Component ◽  
Supporting Evidence ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Large Domain ◽  
Boundary Layer Turbulence ◽  
Power Spectral ◽  
Fine Resolution

Abstract Numerically modeled turbulence simulated by the Advanced Research Weather Research and Forecasting Model (ARW) is evaluated with turbulence measurements from NOAA’s high-resolution Doppler lidar on the NOAA Research Vessel Ronald H. Brown during the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study—Regional Experiment (VOCALS-Rex) field program. A nonprecipitating nocturnal marine stratocumulus case is examined, and a nudging technique is applied to allow turbulence to spin up and come into a statistically stationary state with the initial observed cloud field. This “stationary” state is then used as the initial condition for the subsequent free-running simulation. The comparison shows that the modeled turbulence is consistently weaker than that observed. For the same resolution, the turbulence becomes stronger, especially for the horizontal component, as the length of the horizontal domain increases from 6.4 to 25.6 km. Analysis of the power spectral density shows that, even for the largest domain, the horizontal component of the turbulence is limited by the upper limit of the domain size; supporting evidence from past studies is provided. Results suggest that convergence is expected for (i) energy spectra of turbulence with a sufficiently large domain and (ii) liquid water path with an adequately large domain and fine resolution. Additional tests are performed by changing momentum advection and turning off subgrid-scale diffusion. These exhibit more significant changes in turbulence characteristics compared to the sensitivity to domain size and resolution, suggesting that the model behavior is essentially established by the configuration of the model dynamics and physics and that the simulation only gradually improves when domain size and resolution are increased.

scholarly journals Factors Controlling Rapid Stratocumulus Cloud Thinning

2014 ◽  
Vol 71 (2) ◽  
pp. 655-664 ◽  
Author(s):  
J. J. van der Dussen ◽  
S. R. de Roode ◽  
A. P. Siebesma
Keyword(s):  
Moisture Flux ◽  
Steady State Solution ◽  
Cloud Layer ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Buoyancy Reversal ◽  
Stratocumulus Clouds ◽  
Budget Equation ◽  
Heat And Moisture

Abstract The relationship between the inversion stability and the liquid water path (LWP) tendency of a vertically well-mixed, adiabatic stratocumulus cloud layer is investigated in this study through the analysis of the budget equation for the LWP. The LWP budget is mainly determined by the turbulent fluxes of heat and moisture at the top and the base of the cloud layer, as well as by the source terms due to radiation and precipitation. Through substitution of the inversion stability parameter κ into the budget equation, it immediately follows that the LWP tendency will become negative for increasing values of κ due to the entrainment of increasingly dry air. Large κ values are therefore associated with strong cloud thinning. Using the steady-state solution for the LWP, an equilibrium value κeq is formulated, beyond which the stratocumulus cloud will thin. The Second Dynamics and Chemistry of Marine Stratocumulus field study (DYCOMS-II) is used to illustrate that, depending mainly on the magnitude of the moisture flux at cloud base, stratocumulus clouds can persist well within the buoyancy reversal regime.

scholarly journals Extensive Evaluation of a Continental-Scale High-Resolution Hydrological Model Using Remote Sensing and Ground-Based Observations

2021 ◽  
Vol 13 (7) ◽  
pp. 1247
Author(s):  
Bowen Zhu ◽  
Xianhong Xie ◽  
Chuiyu Lu ◽  
Tianjie Lei ◽  
Yibing Wang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Hydrological Modeling ◽  
Infiltration Capacity ◽  
Modeling Framework ◽  
Large Domain ◽  
Continental Scale ◽  
Extensive Evaluation ◽  
Mean Differences ◽  
Fine Resolution

Extreme hydrologic events are getting more frequent under a changing climate, and a reliable hydrological modeling framework is important to understand their mechanism. However, existing hydrological modeling frameworks are mostly constrained to a relatively coarse resolution, unrealistic input information, and insufficient evaluations, especially for the large domain, and they are, therefore, unable to address and reconstruct many of the water-related issues (e.g., flooding and drought). In this study, a 0.0625-degree (~6 km) resolution variable infiltration capacity (VIC) model developed for China from 1970 to 2016 was extensively evaluated against remote sensing and ground-based observations. A unique feature in this modeling framework is the incorporation of new remotely sensed vegetation and soil parameter dataset. To our knowledge, this constitutes the first application of VIC with such a long-term and fine resolution over a large domain, and more importantly, with a holistic system-evaluation leveraging the best available earth data. The evaluations using in-situ observations of streamflow, evapotranspiration (ET), and soil moisture (SM) indicate a great improvement. The simulations are also consistent with satellite remote sensing products of ET and SM, because the mean differences between the VIC ET and the remote sensing ET range from −2 to 2 mm/day, and the differences for SM of the top thin layer range from −2 to 3 mm. Therefore, this continental-scale hydrological modeling framework is reliable and accurate, which can be used for various applications including extreme hydrological event detections.

scholarly journals Impact of Gravity Waves on Marine Stratocumulus Variability

2012 ◽  
Vol 69 (12) ◽  
pp. 3633-3651 ◽  
Author(s):  
Qingfang Jiang ◽  
Shouping Wang
Keyword(s):  
Gravity Waves ◽  
Vertical Motion ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Large Eddy Simulation Model ◽  
Cloud Albedo ◽  
Eddy Simulation ◽  
Aerosol Number Concentration ◽  
Wave Induced ◽  
The Impact

Abstract The impact of gravity waves on marine stratocumulus is investigated using a large-eddy simulation model initialized with sounding profiles composited from the Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-Rex) aircraft measurements and forced by convergence or divergence that mimics mesoscale diurnal, semidiurnal, and quarter-diurnal waves. These simulations suggest that wave-induced vertical motion can dramatically modify the cloud albedo and morphology through nonlinear cloud–aerosol–precipitation–circulation–turbulence feedback. In general, wave-induced ascent tends to increase the liquid water path (LWP) and the cloud albedo. With a proper aerosol number concentration, the increase in the LWP leads to enhanced precipitation, which triggers or strengthens mesoscale circulations in the boundary layer and accelerates cloud cellularization. Precipitation also tends to create a decoupling structure by weakening the turbulence in the subcloud layer. Wave-induced descent decreases the cloud albedo by dissipating clouds and forcing a transition from overcast to scattered clouds or from closed to open cells. The overall effect of gravity waves on the cloud variability and morphology depends on the cloud property, aerosol concentration, and wave characteristics. In several simulations, a transition from closed to open cells occurs under the influence of gravity waves, implying that some of the pockets of clouds (POCs) observed over open oceans may be related to gravity wave activities.

scholarly journals Precipitation susceptibility in marine stratocumulus and shallow cumulus from airborne measurements

2016 ◽  
Vol 16 (17) ◽  
pp. 11395-11413 ◽  
Author(s):  
Eunsil Jung ◽  
Bruce A. Albrecht ◽  
Armin Sorooshian ◽  
Paquita Zuidema ◽  
Haflidi H. Jonsson
Keyword(s):  
Marine Boundary Layer ◽  
Qualitative Behavior ◽  
Liquid Water Path ◽  
Cumulus Clouds ◽  
Marine Stratocumulus ◽  
Airborne Measurements ◽  
Boundary Layer Clouds ◽  
Shallow Cumulus ◽  
Stratocumulus Clouds ◽  
Field Campaigns

Abstract. Precipitation tends to decrease as aerosol concentration increases in warm marine boundary layer clouds at fixed liquid water path (LWP). The quantitative nature of this relationship is captured using the precipitation susceptibility (So) metric. Previously published works disagree on the qualitative behavior of So in marine low clouds: So decreases monotonically with increasing LWP or cloud depth (H) in stratocumulus clouds (Sc), while it increases and then decreases in shallow cumulus clouds (Cu). This study uses airborne measurements from four field campaigns on Cu and Sc with similar instrument packages and flight maneuvers to examine if and why So behavior varies as a function of cloud type. The findings show that So increases with H and then decreases in both Sc and Cu. Possible reasons for why these results differ from those in previous studies of Sc are discussed.

scholarly journals Detection and characterization of drizzle cells within marine stratocumulus using AMSR-E 89 GHz passive microwave measurements

2012 ◽  
Vol 5 (4) ◽  
pp. 4571-4597
Author(s):  
M. A. Miller ◽  
S. E. Yuter
Keyword(s):  
Brightness Temperature ◽  
Liquid Water ◽  
Cell Number ◽  
Passive Microwave ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Data Set ◽  
Local Maxima ◽  
Spatial Coverage ◽  
Background Brightness

Abstract. This empirical study demonstrates the feasibility of using 89 GHz Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E) passive microwave brightness temperature data to detect heavily drizzling cells within marine stratocumulus. A binary heavy drizzle product is described that can be used to determine areal and feature statistics of drizzle cells within the major marine stratocumulus regions. Current satellite liquid water path (LWP) and cloud radar products capable of detecting drizzle are either lacking in resolution (AMSR-E LWP), diurnal coverage (MODIS LWP), or spatial coverage (CloudSat). The AMSR-E 89 GHz data set at 6 × 4 km spatial resolution is sufficient for resolving individual heavily drizzling cells. Radiant emission at 89 GHz by liquid-water cloud and precipitation particles from drizzling cells in marine stratocumulus regions yields local maxima in brightness temperature against an otherwise cloud-free background brightness temperature. The background brightness temperature is primarily constrained by column-integrated water vapor and sea surface temperature. Clouds containing ice are screened out. Once heavily drizzling pixels are identified, connected pixels are grouped into discrete drizzle cell features. The identified drizzle cells are used in turn to determine several spatial statistics for each satellite scene, including drizzle cell number and size distribution. The identification of heavily drizzling cells within marine stratocumulus regions with satellite data facilitates analysis of seasonal and regional drizzle cell occurrence and the interrelation between drizzle and changes in cloud fraction.

scholarly journals The effects of timing and rate of marine cloud brightening aerosol injection on albedo changes during the diurnal cycle of marine stratocumulus clouds

2013 ◽  
Vol 13 (3) ◽  
pp. 1659-1673 ◽  
Author(s):  
A. K. L. Jenkins ◽  
P. M. Forster ◽  
L. S. Jackson
Keyword(s):  
Point Source ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Early Morning ◽  
Injection Time ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Cloud Albedo ◽  
Aerosol Effect ◽  
Early Afternoon

Abstract. The marine-cloud brightening geoengineering technique has been suggested as a possible means of counteracting the positive radiative forcing associated with anthropogenic atmospheric CO2 increases. The focus of this study is to quantify the albedo response to aerosols injected into marine stratocumulus cloud from a point source at different times of day. We use a cloud-resolving model to investigate both weakly precipitating and non-precipitating regimes. Injection into both regimes induces a first indirect aerosol effect. Additionally, the weakly precipitating regime shows evidence of liquid water path gain associated with a second indirect aerosol effect that contributes to a more negative radiative forcing, and cloud changes indicative of a regime change to more persistent cloud. This results in a cloud albedo increase up to six times larger than in the non-precipitating case. These indirect effects show considerable variation with injection at different times in the diurnal cycle. For the weakly precipitating case, aerosol injection results in domain average increases in cloud albedo of 0.28 and 0.17 in the early and mid morning (03:00:00 local time (LT) and 08:00:00 LT respectively) and 0.01 in the evening (18:00:00 LT). No cloud develops when injecting into the cloud-free early afternoon (13:00:00 LT). However, the all-sky albedo increases (which include both the indirect and direct aerosol effects) are highest for early morning injection (0.11). Mid-morning and daytime injections produce increases of 0.06, with the direct aerosol effect compensating for the lack of cloud albedo perturbation during the cloud-free early afternoon. Evening injection results in an increase of 0.04. For the weakly precipitating case considered, the optimal injection time for planetary albedo response is the early morning. Here, the cloud has more opportunity develop into a more persistent non-precipitating regime prior to the dissipative effects of solar heating. The effectiveness of the sea-spray injection method is highly sensitive to diurnal injection time and the direct aerosol effect of an intense aerosol point source. Studies which ignore these factors could overstate the effectiveness of the marine cloud brightening technique.

scholarly journals Meteorological and Aerosol Effects on Marine Stratocumulus

2016 ◽  
Vol 73 (2) ◽  
pp. 807-820 ◽  
Author(s):  
Zhe Li ◽  
Huiwen Xue ◽  
Jen-Ping Chen ◽  
Wei-Chyung Wang
Keyword(s):  
Precipitation Amount ◽  
Wrf Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Diurnal Cycles ◽  
Microphysical Properties ◽  
Southeastern Pacific ◽  
Lower Cloud

Abstract This study investigates the effects of meteorological conditions and aerosols on marine stratocumulus in the southeastern Pacific using the Weather Research and Forecasting (WRF) Model. Two regimes with different temperature and moisture conditions in the finest model domain are investigated. The western regime is around 87°–79°W, while the eastern regime is around 79°–71°W. In both regimes, cloud fraction, liquid water path (LWP), cloud thickness, and precipitation show significant diurnal cycles. Cloud fraction can be 0.83 during the night and down to 0.29 during the day in the western regime. The diurnal cycles in the eastern regime have smaller amplitudes but are still very strong. Stratocumulus properties also differ in the two regimes. Compared to the western regime, the eastern regime has lower temperature, higher relative humidity, and a more coupled boundary layer, leading to higher cloud fraction (by 0.11) and lower cloud-base height. The eastern regime also has lower inversion height that causes lower cloud-top height and thinner clouds and, hence, lower LWP and less precipitation. Cloud microphysical properties are very sensitive to aerosols in both regimes. Increasing aerosols greatly increase cloud number concentration, decrease cloud effective radius, and suppress precipitation. Cloud macrophysical properties (cloud fraction, LWP) are not sensitive to aerosols in either regime, most notably in the eastern regime where precipitation amount is less. The changes in cloud fraction and LWP caused by changes in aerosol concentrations are smaller than the changes in the diurnal cycle and the spatial variability between the two regimes.

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