Cumulus mergers in the maritime continent region

Simpson, Joanne; Keenan, T. D.; Ferrier, Brad S.; Simpson, R. H.; Holland, Greg J.

doi:10.1007/bf01080881

Cited by 113 publications

(77 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…50 m s −1 represents a very high updraught, but one that is within the range of those inferred from observations of tropical deep convection in other tropical regions (e.g. Simpson et al, 1993). The 10 dBZ echotop also reduces in height with cloud intensity from a maximum of 18.2 km to a minimum of 16.4 km in the "3D-weak" case.…”

Section: Meteorology and Model Initialisationsupporting

confidence: 77%

A study of the effect of overshooting deep convection on the water content of the TTL and lower stratosphere from Cloud Resolving Model simulations

et al. 2007

View full text Add to dashboard Cite

Abstract. Simulations of overshooting, tropical deep convection using a Cloud Resolving Model with bulk microphysics are presented in order to examine the effect on the water content of the TTL (Tropical Tropopause Layer) and lower stratosphere. This case study is a subproject of the HIBISCUS (Impact of tropical convection on the upper troposphere and lower stratosphere at global scale) campaign, which took place in Bauru, Brazil (22 • S, 49 • W), from the end of January to early March 2004.Comparisons between 2-D and 3-D simulations suggest that the use of 3-D dynamics is vital in order to capture the mixing between the overshoot and the stratospheric air, which caused evaporation of ice and resulted in an overall moistening of the lower stratosphere. In contrast, a dehydrating effect was predicted by the 2-D simulation due to the extra time, allowed by the lack of mixing, for the ice transported to the region to precipitate out of the overshoot air.Three different strengths of convection are simulated in 3-D by applying successively lower heating rates (used to initiate the convection) in the boundary layer. Moistening is produced in all cases, indicating that convective vigour is not a factor in whether moistening or dehydration is produced by clouds that penetrate the tropopause, since the weakest case only just did so. An estimate of the moistening effect of these clouds on an air parcel traversing a convective region is made based on the domain mean simulated moistening and the frequency of convective events observed by the IPMet (Instituto de Pesquisas Meteorológicas, Universidade Estadual Paulista) radar (S-band type at 2.8 Ghz) to have the same 10 dBZ echo top height as those simulated. These suggest a fairly significant mean moistening of 0.26, 0.13 and 0.05 ppmv in the strongest, medium and weakest cases, respectively, for heights between 16 and 17 km. Since the cold point and WMO (World Meteorological Organization)Correspondence to: D. P. Grosvenor (daniel.grosvenor@manchester.ac.uk) tropopause in this region lies at ∼15.9 km, this is likely to represent direct stratospheric moistening. Much more moistening is predicted for the 15-16 km height range with increases of 0.85-2.8 ppmv predicted. However, it would be required that this air is lofted through the tropopause via the Brewer Dobson circulation in order for it to have a stratospheric effect. Whether this is likely is uncertain and, in addition, the dehydration of air as it passes through the cold trap and the number of times that trajectories sample convective regions needs to be taken into account to gauge the overall stratospheric effect. Nevertheless, the results suggest a potentially significant role for convection in determining the stratospheric water content.Sensitivity tests exploring the impact of increased aerosol numbers in the boundary layer suggest that a corresponding rise in cloud droplet numbers at cloud base would increase the number concentrations of the ice crystals transported to the TTL, which had the effect of reducing the...

show abstract

Section: Meteorology and Model Initialisationsupporting

confidence: 77%

A study of the effect of overshooting deep convection on the water content of the TTL and lower stratosphere from Cloud Resolving Model simulations

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The subsidence layer acts to restrict the island convection at low levels (shallow convection) at its initial stage, similar to the mainland convection. This is consistent with the results from earlier studies (e.g., Simpson et al 1993), which indicated that the island-initiated convection was characterized by widespread shallow convection at its initial stage over the islands.…”

Section: Vertical Velocitysupporting

confidence: 93%

Ensemble Single Column Modeling in the Tropics - Derivation of observed forcing data sets, estimation of observation uncertainty and application to parametrization improvements

Jakob¹

2012

View full text Add to dashboard Cite

The project was carried out in 2 distinct phases. In the first phase we established the general validity of using an ensemble approach to Single Column Modeling (SCM) using the Manus and Nauru sites. In the second phase we derived and applied an ensemble forcing derivation technique to observations. First we derived an ensemble forcing estimate for the TWP-ICE experiment and then by extended the method to provide three wet seasons of "continuous ensemble forcing" for the Darwin site. The main purpose of using ensemble techniques in SCM simulation is to be able to assess how much of the overall SCM simulation error is due to model errors and how much due to errors in the forcing. Below we briefly summarize the main results of the entire project. All relevant publications are appended to this report. Step 1: Establish the ESCM techniqueUsing NWP re-analysis products we first derived forcing data sets for SCM models over the TWP sites of Manus and Nauru. We thoroughly evaluated the quality of the derived data sets against observations from radiosondes at the sites. We then applied the derived forcing data sets to two SCMs to identify the main source of uncertainties resulting from forcing data in SCM studies. We conclusively showed that it is mainly the boundary conditions, and not as previously thought the initial conditions, that drive uncertainties in SCMs. We further showed that the ensemble methodology does allow to separate model error from forcing errors. The results of this part of the study are summarized in Hume and Jakob (2005, attached) Step 2: Use the ESCM technique in model evaluationHaving established the ESCM technique, we applied it to the evaluation of the BMRC SCM to demonstrate how ensemble techniques can be combined with regime-oriented model evaluation and probabilistic model evaluation techniques to identify model errors and to separate them from errors in the prescribed forcing. We also applied the technique to assess possible modifications to the parametrization of convection in the ECWMF model. We showed that the ESCM techniques is capable of clearly identifying the effect of the changes on the model results, an important characteristic in its application to judge model improvements. The result of this part of the study are summarized in Hume and Jakob (2007, attached).Step 3: Derive best-estimate forcing data sets for TWP-ICEThe TWP-ICE experiment in Jan/Feb 2006 in Darwin spent much effort taking observations to derive forcing data sets for SCM studies. The data collected during the experiment provided the foundation for the main thrust of the research over the second phase of the project. As outlined above, the purpose of the research was to assess the uncertainties in the derivation of SCM forcing data and to provide an alternative methodology of SCM simulations based on ensemble techniques that inherently include the uncertainties in the forcing data sets and hence allow us to estimate the uncertainties in the model results directly resulting from forcing errors. The first step t...

show abstract

“…It is obvious from everyday experience that many clouds do not follow a simple, scripted lifecycle. Many isolated clouds are the result of splits from larger clouds or the merger of two smaller clouds at some previous time [28][29][30][31]. These types of complex evolutions lack a sufficient conceptual place within the standard evolutionary pathway.…”

Section: Introductionmentioning

confidence: 99%

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Igel

2018

Atmosphere

View full text Add to dashboard Cite

Abstract:The tropical, oceanic mean relationship between column relative humidity and precipitation is highly non-linear. Mean precipitation remains weak until it rapidly picks up and grows at high column humidity. To investigate the origin of this relationship, a Lagrangian cloud tracking code, RAMStracks, is developed, which can follow the evolution of clouds. RAMStracks can record the morphological properties of convective clouds, the meteorological environment of clouds, and their effects. RAMStracks is applied to a large-domain radiative convective equilibrium simulation, which produces a complex population of convective clouds. RAMStracks records the lifecycle of 501 clouds through growth, splits, mergers, and decay. The mean evolution of all these clouds is examined. It is shown that the column humidity evolves non-monotonically, but that lower-level and upper-level contributions to total moisture do evolve monotonically. The precipitation efficiency of tropical storms tends to increase with cloud age. This is confirmed using a prototype testing method. The same method reveals that different tracked clouds with similar initial conditions evolve in very different ways. This makes drawing general conclusions from individual storms difficult. Finally, the causality of the precipitation-column humidity relationship is examined. A Granger Causality test, as well as regressions, suggest that moisture and precipitation are causally linked, but that the direction of causality is ambiguous. Much of this link appears to come from the lower-level moisture's contribution to column humidity.

show abstract

Cumulus mergers in the maritime continent region

Cited by 113 publications

References 32 publications

A study of the effect of overshooting deep convection on the water content of the TTL and lower stratosphere from Cloud Resolving Model simulations

A study of the effect of overshooting deep convection on the water content of the TTL and lower stratosphere from Cloud Resolving Model simulations

Ensemble Single Column Modeling in the Tropics - Derivation of observed forcing data sets, estimation of observation uncertainty and application to parametrization improvements

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Contact Info

Product

Resources

About