Folkins, Ian
Permanent URI for this collectionhttps://hdl.handle.net/10222/22066
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Item Open Access Testing convective transport on short time scales: Comparisons with mass divergence and ozone anomaly patterns about high rain events(2012-01) Mitovski, Toni; Folkins, Ian; Martin, Randall V.; Cooper, MatthewNo abstract available.Item Open Access Large-scale enhancements in NO/NOy from subsonic aircraft emissions: Comparisons with observations(1997-12) Witte, JC; Folkins, IA; Neima, J.; Ridley, BA; Walega, JG; Weinheimer, AJNo abstract available.Item Open Access Temperature, relative humidity, and divergence response to high rainfall events in the tropics: Observations and models(American Meteorological Society, 2010) Mitovski, Toni; Folkins, Ian; von Salzen, Knut; Sigmond, MichaelRadiosonde measurements and Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall are used to construct composite anomaly patterns of temperature, relative humidity, and divergence about high rainfall events in the western Pacific. The observed anomaly patterns are compared with anomaly patterns from four general circulation models Third and Fourth Generation Atmospheric General Circulation Model (AGCM3 and AGCM4), Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 (GFDL CM2.1), and European Center Hamburg Model version 5 (ECHAM5)] and two reanalysis products 40-yr ECMWF Re-Analysis (ERA-40) and ERA-Interim]. In general, the models and reanalyses do not fully represent the timing, strength, or altitude of the midlevel congestus divergence that precedes peak rainfall or the midlevel stratiform convergence that occurs after peak rainfall. The surface cold pools that develop in response to high rainfall events are also either not present or somewhat weaker than observations. Surface cold pools originate from the downward transport within mesoscale downdrafts of midtropospheric air with low moist static energy into the boundary layer. Differences between the modeled and observed response to high rainfall events suggest that the convective parameterizations used by the models and reanalyses discussed here may under-represent the strength of the mesoscale downdraft circulation. 2010 American Meteorological Society.Item Open Access Item Open Access Ozone and potential vorticity at the subtropical tropopause break(1996-08) Folkins, I.; Appenzeller, C.No abstract available.Item Open Access Tropical rainfall and boundary layer moist entropy(2003-06) Folkins, I.; Braun, C.No abstract available.Item Open Access Estimating the contribution of bromoform to stratospheric bromine and its relation to dehydration in the tropical tropopause layer(2006-10) Sinnhuber, B. -M; Folkins, I.No abstract available.Item Open Access Space-based constraints on the production of nitric oxide by lightning(2007-05) Martin, Randall V.; Sauvage, Bastien; Folkins, Ian; Sioris, Christopher E.; Boone, Christopher; Bernath, Peter; Ziemke, JerryNo abstract available.Item Open Access Chemistry of the 1991-1992 Stratospheric Winter - 3-Dimensional Model Simulations(1994-04) LEFEVRE, F.; BRASSEUR, GP; FOLKINS, I.; SMITH, AK; SIMON, P.No abstract available.Item Open Access Tropical Tropopause Layer(2009-02) Fueglistaler, S.; Dessler, A. E.; Dunkerton, T. J.; Folkins, I.; Fu, Q.; Mote, P. W.No abstract available.Item Open Access Seasonal cycles of O-3, CO, and convective outflow at the tropical tropopause(2006-08) Folkins, Ian; Bernath, P.; Boone, C.; Lesins, G.; Livesey, N.; Thompson, A. M.; Walker, K.; Witte, J. C.No abstract available.Item Open Access A low-level circulation in the tropics(American Meteorological Society, 2008) Folkins, Ian; Fueglistaler, S.; Lesins, G.; Mitovski, T.Deep convective tropical systems are strongly convergent in the midtroposphere. Horizontal wind measurements from a variety of rawinsonde arrays in the equatorial Pacific and Caribbean are used to calculate the mean dynamical divergence profiles of large-scale 1000 km in diameter) in actively convecting regions. Somewhat surprisingly, the magnitude of the midtropospheric divergence calculated from these arrays is usually small. In principle, the midlevel convergence of deep convective systems could be balanced on larger scales either by a vertical variation in the radiative mass flux of the background clear sky atmosphere, or by a divergence from shallow cumuli. The vertical variation of the clear sky mass flux in the midtroposphere is small, however, so that the offsetting divergence must be supplied by shallow cumuli. On spatial scales 1000 km, the midlevel convergent inflow toward deep convection appears to be internally compensated, or "screened," by a divergent outflow from surrounding precipitating shallow convection. Deep convective systems do not induce a large-scale inflow of midlevel air toward actively convecting regions from the rest of the tropics, but instead help generate a secondary low-level circulation, in which the net downward mass flux from mesoscale and convective-scale downdrafts is balanced by a net upward mass flux from precipitating shallow cumuli. The existence of this circulation is consistent with observational evidence showing that deep and shallow convection are spatiotemporally coupled on a wide range of both spatial and temporal scales. One of the mechanisms proposed for coupling shallow convection to deep convection is the tendency for deep convection to cool the lower troposphere. The authors use radiosonde temperature profiles and the Tropical Rainfall Measuring Mission (TRMM) 3B42 gridded rainfall product to argue that the distance over which deep convection cools the lower troposphere is approximately 1000 km. 2008 American Meteorological Society.Item Open Access Convective damping of buoyancy anomalies and its effect on lapse rates in the tropical lower troposphere(2006-01) Folkins, I.No abstract available.Item Open Access Item Open Access 3-Dimensional Model Interpretation of Nox Measurements from the Lower Stratosphere(1994-11) FOLKINS, I.; WEINHEIMER, AJ; BRASSEUR, G.; LEFEVRE, F.; RIDLEY, BA; WALEGA, JG; COLLINS, JE; PUESCHEL, RFNo abstract available.Item Open Access A one-dimensional cloud model with trimodal convective outflow(American Meteorological Society, 2009) Folkins, IanThe author describes a one-dimensional cloud model designed to investigate the relationships between stratiform downdrafts, congestus outflow, stability, and relative humidity in the tropical lower troposphere. In the tropics, the climatological lapse rate varies with height below the melting level in a way that is inconsistent with the assumptions of either moist pseudoadiabatic or reversible adiabatic ascent. This anomalous variation is referred to as the melting-level stability anomaly (MLSA). It is argued that the MLSA is caused by a transition from static to dynamic downdrafts at the melting level. Above the melting level, evaporation of precipitation cools and moistens the tropical atmosphere but does not generate downdraft parcels with sufficient negative buoyancy to descend between model levels. Below the melting level, the evaporative cooling associated with stratiform precipitation is strong enough to overcome the stability of the atmosphere and generate a convective-scale circulation. The vertical descent within these downdrafts induces a compensatory ascent in the background atmosphere that changes the overall cooling-to-moistening downdraft ratio. The inclusion of this stratiform downdraft circulation brings the modeled lapse rate and relative humidity profiles into simultaneous agreement with observations. The transition from static to dynamic downdrafts is triggered, in the model, by imposed increases in the amount of rain falling outside clouds, in the out-of-cloud rain rate, and in the vertical coherence of the rain shafts. The destabilization of the lower tropical atmosphere triggered by the stratiform circulation affects the development of convective clouds. In particular, the melting-level stability anomaly increases detrainment near the melting level and gives rise to the congestus mode. 2009 American Meteorological Society.Item Open Access Tropical convective outflow and near surface equivalent potential temperatures(2000-08) Folkins, I.; Oltmans, SJ; Thompson, AMNo abstract available.Item Open Access Testing convective parameterizations with tropical measurements of HNO3, CO, H2O, and O-3: Implications for the water vapor budget(2006-12) Folkins, Ian; Bernath, P.; Boone, C.; Donner, L. J.; Eldering, A.; Lesins, Glen; Martin, R. V.; Sinnhuber, B. -M; Walker, K.No abstract available.Item Open Access Origin of lapse rate changes in the upper tropical troposphere(American Meteorological Society, 2002) Folkins, IanVertical motions in clouds arise from a variety of thermodynamic processes, including latent heat release, evaporative cooling, melting, and cloud radiative heating. In the Tropics, the net upward vertical mass flux from convective systems should approximately balance subsidence in clear sky regions associated with radiative cooling, provided the exchange of mass with midlatitudes can be assumed small. Tropical climatologies of temperature, water vapor, and ozone are used to calculate the clear sky radiative mass flux, and the derivative of this mass flux with respect to potential temperature, dMr (x)/dx, is used as a proxy for net convective outflow. Convective outflow increases rapidly at 345 K (~11.3 km). This corresponds to the pseudoequivalent potential temperature xe at which air parcels near the surface first attain positive convective available potential energy (CAPE). The rate at which dMr(x)/dx decreases above 345 K is similar to the rate at which the near surface xe probability distribution function (PDF) decreases. This behavior is referred to as "scaling." It suggests that the timescale for removal of an air parcel from the convective boundary layer is independent of xe (once it has positive CAPE), and that the residual vertical mass flux from convective clouds can be described as if air parcels detrain near their level of neutral buoyancy (LNB). It is also suggested that the mean tropical temperature profile above 345 K is controlled, not by mixing, but by the need for the vertical variation in net convective outflow to be consistent with the near-surface xe PDF, and that this accounts for the fact that the mean temperature profile above 345 K increasingly deviates from a moist adiabat. It is also argued that there are sufficient high xe air parcels near the surface to sustain the Brewer-Dobson circulation by detrainment at the LNB followed by radiative ascent into the stratosphere.Item Open Access