scholarly journals Analysis of Convective Transport and Parameter Sensitivity in a Single Column Version of the Goddard Earth Observation System, Version 5, General Circulation Model

2009 ◽  
Vol 66 (3) ◽  
pp. 627-646 ◽  
Author(s):  
L. E. Ott ◽  
J. Bacmeister ◽  
S. Pawson ◽  
K. Pickering ◽  
G. Stenchikov ◽  
...  
Keyword(s):  
Mass Flux ◽  
General Circulation ◽  
Parameter Sensitivity ◽  
Convective Transport ◽  
Trace Gas ◽  
Gas Mixing ◽  
Mixing Ratios ◽  
Mass Fluxes ◽  
Single Column ◽  
Convective Mass Flux

Abstract Convection strongly influences the distribution of atmospheric trace gases. General circulation models (GCMs) use convective mass fluxes calculated by parameterizations to transport gases, but the results are difficult to compare with trace gas observations because of differences in scale. The high resolution of cloud-resolving models (CRMs) facilitates direct comparison with aircraft observations. Averaged over a sufficient area, CRM results yield a validated product directly comparable to output from a single global model grid column. This study presents comparisons of vertical profiles of convective mass flux and trace gas mixing ratios derived from CRM and single column model (SCM) simulations of storms observed during three field campaigns. In all three cases, SCM simulations underpredicted convective mass flux relative to CRM simulations. As a result, the SCM simulations produced lower trace gas mixing ratios in the upper troposphere in two of the three storms than did the CRM simulations. The impact of parameter sensitivity in the moist physics schemes employed in the SCM has also been examined. Statistical techniques identified the most significant parameters influencing convective transport. Convective mass fluxes are shown to be strongly dependent on chosen parameter values. Results show that altered parameter settings can substantially improve the comparison between SCM and CRM convective mass flux. Upper tropospheric trace gas mixing ratios were also improved in two storms. In the remaining storm, the SCM representation of CO2 was not improved because of differences in entrainment and detrainment levels in the CRM and SCM simulations.

scholarly journals Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O3photostationary state and peroxy radical levels

2012 ◽  
Vol 117 (D5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Ivonne Trebs ◽  
Olga L. Mayol-Bracero ◽  
Theotonio Pauliquevis ◽  
Uwe Kuhn ◽  
Rolf Sander ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Peroxy Radical ◽  
Trace Gas ◽  
Gas Mixing ◽  
Mixing Ratios ◽  
Urban Plume

scholarly journals Modelling the reversible uptake of chemical species in the gas phase by ice particles formed in a convective cloud

2010 ◽  
Vol 10 (10) ◽  
pp. 4977-5000 ◽  
Author(s):  
V. Marécal ◽  
M. Pirre ◽  
E. D. Rivière ◽  
N. Pouvesle ◽  
J. N. Crowley ◽  
...  
Keyword(s):  
Cloud Model ◽  
Laboratory Data ◽  
Chemical Species ◽  
Trace Gas ◽  
Limiting Factor ◽  
Gas Mixing ◽  
Mixing Ratios ◽  
Ice Particles ◽  
Cloud Resolving Model ◽  
Single Moment

Abstract. The present paper is a preliminary study preparing the introduction of reversible trace gas uptake by ice particles into a 3-D cloud resolving model. For this a 3-D simulation of a tropical deep convection cloud was run with the BRAMS cloud resolving model using a two-moment bulk microphysical parameterization. Trajectories within the convective clouds were computed from these simulation outputs along which the variations of the pristine ice, snow and aggregate mixing ratios and concentrations were extracted. The reversible uptake of 11 trace gases by ice was examined assuming applicability of Langmuir isotherms using recently evaluated (IUPAC) laboratory data. The results show that ice uptake is only significant for HNO3, HCl, CH3COOH and HCOOH. For H2O2, using new results for the partition coefficient results in significant partitioning to the ice phase for this trace gas also. It was also shown that the uptake is largely dependent on the temperature for some species. The adsorption saturation at the ice surface for large gas mixing ratios is generally not a limiting factor except for HNO3 and HCl for gas mixing ratio greater than 1 ppbv. For HNO3, results were also obtained using a trapping theory, resulting in a similar order of magnitude of uptake, although the two approaches are based on different assumptions. The results were compared to those obtained using a BRAMS cloud simulation based on a single-moment microphysical scheme instead of the two moment scheme. We found similar results with a slightly more important uptake when using the single-moment scheme which is related to slightly higher ice mixing ratios in this simulation. The way to introduce these results in the 3-D cloud model is discussed.

scholarly journals Stratospheric dryness: model simulations and satellite observations

2007 ◽  
Vol 7 (5) ◽  
pp. 1313-1332 ◽  
Author(s):  
J. Lelieveld ◽  
C. Brühl ◽  
P. Jöckel ◽  
B. Steil ◽  
P. J. Crutzen ◽  
...  
Keyword(s):  
Water Vapor ◽  
General Circulation ◽  
Large Scale ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Satellite Observations ◽  
Radiative Heating ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Mass Fluxes

Abstract. The mechanisms responsible for the extreme dryness of the stratosphere have been debated for decades. A key difficulty has been the lack of comprehensive models which are able to reproduce the observations. Here we examine results from the coupled lower-middle atmosphere chemistry general circulation model ECHAM5/MESSy1 together with satellite observations. Our model results match observed temperatures in the tropical lower stratosphere and realistically represent the seasonal and inter-annual variability of water vapor. The model reproduces the very low water vapor mixing ratios (below 2 ppmv) periodically observed at the tropical tropopause near 100 hPa, as well as the characteristic tape recorder signal up to about 10 hPa, providing evidence that the dehydration mechanism is well-captured. Our results confirm that the entry of tropospheric air into the tropical stratosphere is forced by large-scale wave dynamics, whereas radiative cooling regionally decelerates upwelling and can even cause downwelling. Thin cirrus forms in the cold air above cumulonimbus clouds, and the associated sedimentation of ice particles between 100 and 200 hPa reduces water mass fluxes by nearly two orders of magnitude compared to air mass fluxes. Transport into the stratosphere is supported by regional net radiative heating, to a large extent in the outer tropics. During summer very deep monsoon convection over Southeast Asia, centered over Tibet, moistens the stratosphere.

scholarly journals Mesoscale convective systems observed during AMMA and their impact on the NO<sub>x</sub> and O<sub>3</sub> budget over West Africa

2010 ◽  
Vol 10 (10) ◽  
pp. 22765-22853
Author(s):  
H. Huntrieser ◽  
H. Schlager ◽  
M. Lichtenstern ◽  
P. Stock ◽  
T. Hamburger ◽  
...  
Keyword(s):  
Production Rate ◽  
Mass Flux ◽  
Mesoscale Convective Systems ◽  
Trace Gas ◽  
Stroke Rate ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Convective Core ◽  
Different Types ◽  
Mesoscale Convective

Abstract. During the "African Monsoon Multidisciplinary Analysis" (AMMA) field phase in August 2006, a variety of measurements focusing on deep convection were performed over West Africa. The German research aircraft Falcon based in Ouagadougou (Burkina Faso) investigated the chemical composition in the outflow of large mesoscale convective systems (MCS). Here we analyse two different types of MCS originating north and south of the intertropical convergence zone (ITCZ, ~10° N), respectively. In addition to the airborne trace gas measurements, stroke measurements from the Lightning Location Network (LINET), set up in Northern Benin, are analysed. The main focus of the present study is 1) to analyse the trace gas composition (CO, O3, NO, NOx, NOy, and HCHO) in the convective outflow as a function of distance from the convective core, 2) to investigate how different trace gas compositions in the boundary layer (BL) and ambient air may influence the O3 concentration in the convective outflow, and 3) to estimate the rate of lightning-produced nitrogen oxides per flash in selected thunderstorms and compare it to our previous results for the tropics. The MCS outflow was probed at different altitudes (~10–12 km) and distances from the convective core (<500 km). Trace gas signatures similar to the conditions in the MCS inflow region were observed in the outflow close to the convective core, due to efficient vertical transport. In the fresh MCS outflow, low O3 mixing ratios in the range of 35–40 nmol mol−1 were observed. Further downwind, O3 mixing ratios in the outflow rapidly increased with distance, due to mixing with the ambient O3-rich air. After 2–3 h, O3 mixing ratios in the range of ~65 nmol mol−1 were observed in the aged outflow. Within the fresh MCS outflow, mean NOx (=NO+NO2) mixing ratios were in the range of ~0.3–0.4 nmol mol−1 (peaks ~1 nmol mol−1) and only slightly enhanced compared to the background. Both lightning-produced NOx (LNOx) and NOx transported upward from the BL contributed about equally to this enhancement. On the basis of Falcon measurements, the mass flux of LNOx in the investigated MCS was estimated to be ~100 g(N) s−1. The average stroke rate of the probed thunderstorms was 0.04–0.07 strokes s−1 (here only strokes with peak currents ≥10 kA contributing to LNOx were considered). The LNOx mass flux and the stroke rate were combined to estimate the LNOx production rate. For a better comparison with other published results, LNOx estimates per LINET stroke were scaled to Lightning Imaging Sensor (LIS) flashes. The LNOx production rate per LIS flash was estimated to 1.0 and 2.5 kg(N) for the MCS located south and north of the ITCZ, respectively. If we assume, that these different types of MCS are typical thunderstorms occurring globally (LIS flash rate ~44 s−1), the annual global LNOx production rate was estimated to be ~1.4 and 3.5 Tg(N) a−1.

scholarly journals Deep-convective vertical transport: what is mass flux?

2009 ◽  
Vol 9 (1) ◽  
pp. 3535-3553 ◽  
Author(s):  
J.-I. Yano
Keyword(s):  
Mass Flux ◽  
Vertical Profile ◽  
Historical Perspective ◽  
Chemical Species ◽  
Main Idea ◽  
Chemical Transport ◽  
Convective Transport ◽  
Point Of View ◽  
Vertical Profiles ◽  
Convective Mass Flux

Abstract. Conceptual basis for the convective mass flux that is used in parameterizations is reviewed from a historical perspective. The main idea of the convective mass flux formulation does not purely reside in dividing the grid-box averaged vertical velocity into several mass flux components such as convective updrafts, downdrafts, and environmental subsidence. The main point rather resides on assuming different vertical profiles for transported quantities for different components. From this point of view, the best way to turn off the convective transport of chemical species is to set the vertical profile of chemical species within convective components (both updrafts and downdrafts) equal to that of the environment. This procedure turns out to be equivalent of simply turning off a standard convective chemical transport package.

scholarly journals Evaluation of cloud convection and tracer transport in a three-dimensional chemical transport model

2011 ◽  
Vol 11 (12) ◽  
pp. 5783-5803 ◽  
Author(s):  
W. Feng ◽  
M. P. Chipperfield ◽  
S. Dhomse ◽  
B. M. Monge-Sanz ◽  
X. Yang ◽  
...  
Keyword(s):  
Mass Flux ◽  
Large Scale ◽  
Transport Model ◽  
Chemical Transport ◽  
Convective Transport ◽  
Convective Precipitation ◽  
Tracer Transport ◽  
Chemical Transport Model ◽  
Mass Fluxes ◽  
Spatial And Seasonal Variation

Abstract. We investigate the performance of cloud convection and tracer transport in a global off-line 3-D chemical transport model. Various model simulations are performed using different meteorological (re)analyses (ERA-40, ECMWF operational and ECMWF Interim) to diagnose the updraft mass flux, convective precipitation and cloud top height. The diagnosed upward mass flux distribution from TOMCAT agrees quite well with the ECMWF reanalysis data (ERA-40 and ERA-Interim) below 200 hPa. Inclusion of midlevel convection improves the agreement at mid-high latitudes. However, the reanalyses show strong convective transport up to 100 hPa, well into the tropical tropopause layer (TTL), which is not captured by TOMCAT. Similarly, the model captures the spatial and seasonal variation of convective cloud top height although the mean modelled value is about 2 km lower than observed. The ERA-Interim reanalyses have smaller archived upward convective mass fluxes than ERA-40, and smaller convective precipitation, which is in better agreement with satellite-based data. TOMCAT captures these relative differences when diagnosing convection from the large-scale fields. The model also shows differences in diagnosed convection with the version of the operational analyses used, which cautions against using results of the model from one specific time period as a general evaluation. We have tested the effect of resolution on the diagnosed modelled convection with simulations ranging from 5.6° × 5.6° to 1° × 1°. Overall, in the off-line model, the higher model resolution gives stronger vertical tracer transport, however, it does not make a large change to the diagnosed convective updraft mass flux (i.e., the model results using the convection scheme fail to capture the strong convection transport up to 100 hPa as seen in the archived convective mass fluxes). Similarly, the resolution of the forcing winds in the higher resolution CTM does not make a large improvement compared to the archived mass fluxes. Including a radon tracer in the model confirms the importance of convection for reproducing observed midlatitude profiles. The model run using archived mass fluxes transports significantly more radon to the upper troposphere but the available data does not strongly discriminate between the different model versions.

scholarly journals Behavior of trace gas mixing ratios on a very tall tower in North Carolina

1997 ◽  
Vol 102 (D7) ◽  
pp. 8825-8835 ◽  
Author(s):  
Dale F. Hurst ◽  
Peter S. Bakwin ◽  
Richard C. Myers ◽  
James W. Elkins
Keyword(s):  
North Carolina ◽  
Trace Gas ◽  
Gas Mixing ◽  
Mixing Ratios ◽  
Tall Tower

scholarly journals A Lagrangian convective transport scheme including a simulation of the time air parcels spend in updrafts (LaConTra v1.0)

2019 ◽  
Vol 12 (10) ◽  
pp. 4387-4407 ◽  
Author(s):  
Ingo Wohltmann ◽  
Ralph Lehmann ◽  
Georg A. Gottwald ◽  
Karsten Peters ◽  
Alain Protat ◽  
...  
Keyword(s):  
General Circulation ◽  
Fixed Time ◽  
Analysis Data ◽  
Convective Transport ◽  
Tropospheric Chemistry ◽  
Area Fraction ◽  
Time Step ◽  
Variable Time ◽  
Mass Fluxes ◽  
Meteorological Analysis

Abstract. We present a Lagrangian convective transport scheme developed for global chemistry and transport models, which considers the variable residence time that an air parcel spends in convection. This is particularly important for accurately simulating the tropospheric chemistry of short-lived species, e.g., for determining the time available for heterogeneous chemical processes on the surface of cloud droplets. In current Lagrangian convective transport schemes air parcels are stochastically redistributed within a fixed time step according to estimated probabilities for convective entrainment as well as the altitude of detrainment. We introduce a new scheme that extends this approach by modeling the variable time that an air parcel spends in convection by estimating vertical updraft velocities. Vertical updraft velocities are obtained by combining convective mass fluxes from meteorological analysis data with a parameterization of convective area fraction profiles. We implement two different parameterizations: a parameterization using an observed constant convective area fraction profile and a parameterization that uses randomly drawn profiles to allow for variability. Our scheme is driven by convective mass fluxes and detrainment rates that originate from an external convective parameterization, which can be obtained from meteorological analysis data or from general circulation models. We study the effect of allowing for a variable time that an air parcel spends in convection by performing simulations in which our scheme is implemented into the trajectory module of the ATLAS chemistry and transport model and is driven by the ECMWF ERA-Interim reanalysis data. In particular, we show that the redistribution of air parcels in our scheme conserves the vertical mass distribution and that the scheme is able to reproduce the convective mass fluxes and detrainment rates of ERA-Interim. We further show that the estimated vertical updraft velocities of our scheme are able to reproduce wind profiler measurements performed in Darwin, Australia, for velocities larger than 0.6 m s−1. SO2 is used as an example to show that there is a significant effect on species mixing ratios when modeling the time spent in convective updrafts compared to a redistribution of air parcels in a fixed time step. Furthermore, we perform long-time global trajectory simulations of radon-222 and compare with aircraft measurements of radon activity.

scholarly journals Mesoscale convective systems observed during AMMA and their impact on the NO<sub>x</sub> and O<sub>3</sub> budget over West Africa

2011 ◽  
Vol 11 (6) ◽  
pp. 2503-2536 ◽  
Author(s):  
H. Huntrieser ◽  
H. Schlager ◽  
M. Lichtenstern ◽  
P. Stock ◽  
T. Hamburger ◽  
...  
Keyword(s):  
Production Rate ◽  
Mass Flux ◽  
Mesoscale Convective Systems ◽  
Trace Gas ◽  
Stroke Rate ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Convective Core ◽  
Different Types ◽  
Mesoscale Convective

Abstract. During the "African Monsoon Multidisciplinary Analysis" (AMMA) field phase in August 2006, a variety of measurements focusing on deep convection were performed over West Africa. The German research aircraft Falcon based in Ouagadougou (Burkina Faso) investigated the chemical composition in the outflow of large mesoscale convective systems (MCS). Here we analyse two different types of MCS originating north and south of the intertropical convergence zone (ITCZ, ~10° N), respectively. In addition to the airborne trace gas measurements, stroke measurements from the Lightning Location Network (LINET), set up in Northern Benin, are analysed. The main focus of the present study is (1) to analyse the trace gas composition (CO, O3, NO, NOx, NOy, and HCHO) in the convective outflow as a function of distance from the convective core, (2) to investigate how different trace gas compositions in the boundary layer (BL) and ambient air may influence the O3 concentration in the convective outflow, and (3) to estimate the rate of lightning-produced nitrogen oxides per flash in selected thunderstorms and compare it to our previous results for the tropics. The MCS outflow was probed at different altitudes (~10–12 km) and distances from the convective core (<500 km). Trace gas signatures similar to the conditions in the MCS inflow region were observed in the outflow close to the convective core, due to efficient vertical transport. In the fresh MCS outflow, low O3 mixing ratios in the range of 35–40 nmol mol−1 were observed. Further downwind, O3 mixing ratios in the outflow rapidly increased with distance, due to mixing with the ambient O3-rich air. After 2–3 h, O3 mixing ratios in the range of ~65 nmol mol−1 were observed in the aged outflow. Within the fresh MCS outflow, mean NOx (=NO+NO2) mixing ratios were in the range of ~0.3–0.4 nmol mol−1 (peaks ~1 nmol mol−1) and only slightly enhanced compared to the background. Both lightning-produced NOx (LNOx) and NOx transported upward from the BL contributed about equally to this enhancement. On the basis of Falcon measurements, the mass flux of LNOx in the investigated MCS was estimated to be ~100 g(N) s−1. The average stroke rate of the probed thunderstorms was 0.04–0.07 strokes s−1 (here only strokes with peak currents ≥10 kA contributing to LNOx were considered). The LNOx mass flux and the stroke rate were combined to estimate the LNOx production rate. For a better comparison with other published results, LNOx estimates per LINET stroke were scaled to Lightning Imaging Sensor (LIS) flashes. The LNOx production rate per LIS flash was estimated to 1.0 and 2.5 kg(N) for the MCS located south and north of the ITCZ, respectively. If we assume, that these different types of MCS are typical thunderstorms occurring globally (LIS flash rate ~44 s−1), the annual global LNOx production rate was estimated to be ~1.4 and 3.5 Tg(N) a−1.

Disturbance of stratospheric trace gas mixing ratios during the MAP/GLOBUS 1983 campaign

1987 ◽  
Vol 35 (5) ◽  
pp. 673-684 ◽  
Author(s):  
D. Offermann ◽  
H. Rippel ◽  
P. Aimedieu ◽  
W.A. Matthews ◽  
G. Mégie ◽  
...  
Keyword(s):  
Trace Gas ◽  
Gas Mixing ◽  
Mixing Ratios
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