Modeling Capabilities & Data Analysis

Sierra maintains a wide variety of emission inventory and air quality models and has extensive experience and expertise in developing as well as implementing these models in regulatory compliance and air quality planning applications.

Mobile Source Models – Sierra has an extensive history with mobile source emission factor, emission inventory and vehicle simulation models – covering both model development and model application.  Models include the U.S. Environmental Protection Agency's (U.S. EPA's) MOVES, MOBILE, and NONROAD series and the California Air Resources Board's (CARB's) EMFAC and OFFROAD series.  Sierra also develops customized versions of MOVES, MOBILE, NONROAD, and EMFAC to address specific clients needs.  In addition, Sierra has adapted and implemented a vehicle simulation model, VEHSIM, for a variety of applications where there is a need to simulate the effects of changes in vehicle and engine design or changes in vehicle driving patterns on emissions and fuel efficiency.  In each of these situations, Sierra has experience both in running these models in regulatory and research/planning applications, and in creating client-specific versions to expand the modeling capabilities beyond those contained in the standard models.

Emission Inventory Processing Models – Sierra has a broad background in emission inventory development/processing in support of regulatory evaluations, air quality planning (e.g., State Implementation Plans [SIP]) and photochemical modeling applications. Inventory processing includes chemical speciation, spatial allocation, spatial surrogate development and temporal allocation.  Source categories include anthropogenic (mobile, area and point) and biogenic sources.  Processing experience includes the use of the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system and the Emissions Preprocessor System (EPS).  Experience also includes the use of U.S. EPA and CARB speciation databases and the SMOKE-MOVES interface, a suite of scripts and Fortran code that generates inputs and runscripts for MOVES, and processes MOVES outputs for use in SMOKE.

Air Dispersion & Photochemical Models – Sierra provides air quality modeling services using a range of U.S. EPA and state guideline models.  Screening and refined modeling is performed in support of air quality permitting, environmental documentation (NEPA and CEQA compliance), and regional and local planning using models such as AERMOD, CAL3QHCR, CALINE3, CALPUFF, CMAQ, CTSCREEN, ISCST3, OCD, RTDM, SCREEN3, and VISCREEN.  Models such as AERMOD, CALPUFF, and ISCST3 require extensive meteorological data sets, which Sierra assembles using software such as AERMET, CALMET, and PCRAMMET.  Sierra also has expertise in the specialized air dispersion models used in hazardous materials offsite consequence modeling, including RMP*Comp, SLAB and DEGADIS.  Sierra has in-depth experience in health risk assessment (HRA) modeling using California's Hot Spots and Assessment Program (HARP) model.  Sierra's modeling experience extends to the use of 3-D photochemical transport models such as CMAQ to simulate regional particulate concentrations in support of State Implementation Plan (SIP) development.  Sierra has also worked with the Meteorology-Chemical Interface Processor (MCIP) program to process Weather Research and Forecasting (WRF) meteorological fields for CMAQ inputs, and with the Mesoscale Model Interface Program (MMIF), a WRF/MM5 met postprocessor that formats outputs for use in CALPUFF and AERMOD.

Data Library – Sierra maintains an extensive library of data resources containing air quality, meteorology, emissions inventory, fuel surveys, and motor vehicle test data for California and a number of other states.  Motor vehicle data include emission control system descriptions (dating from 1973), vehicle emissions test results from surveillance testing and I/M undercover testing conducted by the California Air Resources Board and the U.S. Environmental Protection Agency, and millions of test records from a variety of state I/M programs.

Data Analysis – Sierra has extensive experience in analyzing large volumes of air quality, travel characteristics, fuel quality, and vehicle emissions data using a variety of statistical, database management and GIS tools.  This experience has been applied in a variety of applications, including air quality planning, emission inventory development and forecasting, air quality trend analysis and attainment demonstration, mobile source emission factor model development, transportation planning, and vehicle driving pattern/drive cycle analyses.