The Use of NASA's Modern Era Retrospective-analysis for Research and Applications (MERRA) Data For Assessment of Building Climate Zone Change and Variability Over the Last 30 Years

In the US, residential and commercial building infrastructure combined consumes about 40% of total energy usage and emits about 39% of total CO₂emission (DOE/EIA "Annual Energy Outlook 2013").  Thus, increasing the energy efficiency of buildings is paramount to reducing energy costs and emissions. Building codes, as used by local and state enforcement entities are typically tied to the dominant climate within an enforcement jurisdiction, where the dominant climate is based upon a 30-year average of local to regional surface observations. Guidelines for these codes are developed by DOE and ASHRAE (formerly known as the American Society of Hearting, Refrigeration and Air-Conditioning Engineers). A major emphasis of ASHRAE is the development of standards for the design of residential and commercial buildings in the United States. Based upon surface observations ASHRAE, in partnership with the Department of Energy, have developed climate zone maps.A significant shortcoming of the methodology used in constructing such maps is the use of surface observations that may be far removed from the construction site of interest and from the fact that most surface observation sites are located at airports that may not reflect the environment of the construction site. Additionally, surface observations can frequently have periods of missing data that need to be filled by various approximation schemes.

This paper discusses and assesses the use of the NASA Modern Era Retrospective-analysis for Research and Applications (MERRA) atmospheric data assimilation to derive the ASHRAE climate zone maps.  First we show the uncertainties of the basic surface temperature and precipitation parameters from MERRA used in determining the various climate zones.  Intermediary products require the production of the annual heating/cooling degree days (HDD/CDD).  We also show that MERRA HDD/CDD quantities agree with corresponding quantities based upon surface measurements to within about 4-6% percent.  It is also shown that MERRA surface meteorological data products replicate the interannual variability including observed variability in US regions.  Based upon these results, we assess the variability of the ASHRAE climate zones according to MERRA over the last 30 years (see Figure 1).  This work quantifies and tests for significance the changes seen in the various US regions used for the National Climate Assessment using a modified statistical technique by Weatherhead et al., (1998).  These results show that there is a statistically significant increase in the area covered by warmer climate zones and some tendency for a reduction of area in colder climate zones that require longer time series to confirm.  These data are now being made available on the web through the NASA Prediction of Worldwide Energy Resource (POWER) web site: http://power.larc.nasa.gov.

Fig. 1: ASHRAE/DOE Climate zones based upon MERRA meteorological temperatures averaged over 1981–2011.The zone number is defined in the table below. The thick black lines denote the NCA regional boundaries, which correspond to Northeast (NEast), Southeast (SEast), Middle West (MidWest), Great Plains South (GrtPl-S) and North (GrtPls-N), Southwest (SWest) and Northwest (NWest), respectively. Also shown are trends that meet the test of a 95 percent probability.