The cooling and heating degree day parameters are commonly used in energy consumption studies as they correlate better with energy use than the raw temperature data. The cooling degree day parameter is a useful indicator of summertime air-conditioning energy consumption. It is defined by:       

In this equation N_d is the number of days in the calculation (365 for annual degree day totals), and T is the mean daily temperature. The base temperature, T_b, for degree days is generally defined as 65F (18.3^oC), although other base temperatures are sometimes used. The binary multiplier g_d takes on a value of 1 if the daily temperature is higher than the base, and zero otherwise. Degree day totals are typically given on a monthly or annual basis. In the present work all degree day values are annual totals (N_d=365).

            The heating degree day parameter reflects demand for wintertime space heating. Similar to the above definition for CDD the definition for heating degree days is given  by:

Hence, on a day with a mean temperature of 63 ^oF we would obtain CDD=0 and HDD =2.

            The population parameter represents the role that metropolitan size plays in the spatial extent of mitigation strategies and ozone magnitude/sensitivity. MIST uses Metropolitan Statistical Area (MSA). If a user is interested in exploring application of mitigation strategies over a different area (e.g., city scale) they can change the population parameter accordingly.

8.  Air temperature sensitivity to changes in albedo

            This parameter represents the nominal change in air temperature (deg. C) associated with a 0.1 increase in city-scale albedo. Hence, it has a negative value.

9. Air temperature sensitivity to changes in vegetation cover

            This parameter represents the nominal change in temperature (deg. C) associated with a 0.1 increase in city-scale vegetative cover. Hence, it has a negative value.

10. 1hr ozone sensitivity to average daily temperature

            Since ozone concentrations generally increase with temperature this parameter is generally positive with values around 2 to 4 ppb per ^oC.

11. 8hr ozone sensitivity to average daily temperature

            Since ozone concentrations generally increase with temperature this parameter is generally positive with values around 1 to 3 ppb per ^oC. The 8-hour sensitivity parameter is smaller than the corresponding 1-hour sensitivity factor since averages over the longer time period are smaller.

12. Fractional change in CDD for DT= -1 ^oC

            The calculation of CDD requires detailed daily temperature data for the city of interest. The impact of a temperature perturbation on degree days cannot be calculated directly without use of such daily data. Values of this parameter were obtained directly from observational data for a subset of 20 cities. For other cities it was calculated using a linear regression through these data.

13. Fractional change in HDD for DT= -1 ^oC

The calculation of HDD requires detailed daily temperature data for the city of interest. The impact of a temperature perturbation on degree days cannot be calculated directly without use of such daily data. Values of this parameter were obtained directly from observational data for a subset of 20 cities. For other cities it was calculated using a linear regression through these data.

            For a subset of cities in MIST we obtained the typical peak 1-hour ozone values for the year 2000. These data are used to establish a nominal “current” value of 1-hour ozone concentrations.

Advanced users seeking more detailed information on this and other topics related to the scientific and modeling underpinnings of the MIST software tool should read the detailed model description document that can be downloaded from the MIST website.