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Clara S. Draper, Rolf H. Reichle, and Randal D. Koster

partitioning of incident surface radiation between latent heat (LH) and sensible heat (SH) fluxes back to the atmosphere. Reichle et al. (2017a) show that both MERRA-2 and MERRA-Land have improved upon the land surface hydrology of MERRA, showing better agreement with independent observational time series of soil moisture, terrestrial water storage, streamflow, and snow amount. Here, we extend this work, by evaluating the MERRA-2 surface energy budget and 2-m temperatures over land. In particular, we

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Laura M. Hinkelman

-of-atmosphere (TOA) radiative fluxes and surface temperature in the context of climate variability. Applications of MERRA data for polar studies include the work of La and Park (2016) on the effect of clouds on phytoplankton in Antarctica, as well as a paper by Letterly et al. (2016) concerning the impact of winter clouds on summer sea ice in the Arctic. Hundreds of other papers relying on MERRA data are in the literature. While use of MERRA continues, the number of studies based on MERRA-2 has grown

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Natalie P. Thomas, Michael G. Bosilovich, Allison B. Marquardt Collow, Randal D. Koster, Siegfried D. Schubert, Amin Dezfuli, and Sarith P. Mahanama

the linkage varies regionally ( Koster et al. 2009 ; Cheng et al. 2019 ). Relatively fewer studies have focused on the mechanisms associated with nighttime heat waves. Nighttime heat waves have typically been linked with an anomalously moist atmosphere, which affects downward longwave fluxes. Gershunov et al. (2009) found a similar atmospheric circulation during daytime and nighttime heat waves over California but greater moisture advection from offshore during the latter. In their study of

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Allison B. Marquardt Collow and Mark A. Miller

et al. 2009 ; Parding et al. 2011 ; Miller et al. 2012 ; Collow et al. 2016a ). These studies have produced either heating rate profiles or “bulk” measurements of the net radiative heating of the column, using the vertical cross-atmosphere radiative flux divergence (RFD). The RFD is presented in watts per meter squared and is defined so that net fluxes at the surface and the top of the atmosphere (TOA) are a positive quantity when there is net radiation transfer into the column. This sign

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C. A. Randles, A. M. da Silva, V. Buchard, P. R. Colarco, A. Darmenov, R. Govindaraju, A. Smirnov, B. Holben, R. Ferrare, J. Hair, Y. Shinozuka, and C. J. Flynn

), MERRA-2 overestimates absorption in regions remote from aerosol sources (e.g., the free troposphere) due to excessive amounts of black carbon aerosol in these regions [see Randles et al. (2016) for comparisons of MERRA-2 to black carbon vertical distributions from aircraft observations]. Recall that the DRE is defined as the shortwave flux difference (in W m −2 ) between clear-sky (i.e., no clouds) and clear, clean-sky conditions (i.e., no aerosols or clouds). In the absence of clouds, the

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Lawrence Coy, Paul A. Newman, Steven Pawson, and Leslie R. Lait

direction of the acceleration rather than turning as at midlatitudes. In contrast to the typical downward propagation of the QBO, based on wave-induced accelerations in the regions of vertical wind shear, Newman et al. (2016) and Osprey et al. (2016) found easterlies developing in the region of strong westerlies. Examination of the tropical zonal momentum budget by Osprey et al. (2016) showed that the divergence of the horizontal Eliassen–Palm (EP) flux component (see Andrews et al. 1987 , p. 128

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Richard I. Cullather and Sophie M. J. Nowicki

these data. Previous studies have focused on the presence of intense North Atlantic atmospheric blocking events (e.g., Rajewicz and Marshall 2014 ; Häkkinen et al. 2014 ; McLeod and Mote 2016 ). These conditions may preferentially allow for an enhanced solar radiative flux to reach the ice sheet surface and allow for albedo feedback processes to promote large-scale melting. Alternatively, Bennartz et al. (2013) identified the importance of warm air advection and the role of clouds in

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Allison B. Marquardt Collow, Michael G. Bosilovich, and Randal D. Koster

effort to reduce spatial variability in precipitation within the Northeast region as defined by the National Climate Assessment ( Horton et al. 2014 ). Figures that were used to further define the Northeast region can be seen in the supplemental material. Fig . 1. Mean JJA (a) 2-m temperature, (b) observed precipitation, (c) vertically integrated water vapor flux, and (d) TPW over the period 1980–2014. The Northeast region as defined in this study is outlined in black. Using the CPC gauge

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Franklin R. Robertson, Michael G. Bosilovich, and Jason B. Roberts

satellite observations especially, have a time-dependent ability to correct the model first-guess fields. Therefore discrete biases develop in water and energy fluxes and transports. For reanalyses the vertically integrated atmospheric moisture budget over land grid points is that is, vapor plus condensate W a increases as the result of vertically integrated atmospheric moisture flux convergence (VMFC) and ET and is depleted by precipitation P . In reanalyses, the analysis increment (ANA) represents

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Krzysztof Wargan and Lawrence Coy

compared to the analysis. Some of this underestimate can be traced back to a tendency for the forecasts to underestimate the wave forcing on the stratosphere with respect to MERRA-2. Figure 10 plots the vertical component of the Eliassen–Palm (EP) flux at 100 hPa during January–February 2009 for both MERRA-2 and the 23 forecasts. Here the vertical EP flux (based only on the meridional heat flux, as the vertical momentum flux is negligibly small for the planetary scale waves of interest) is calculated

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