286
V. Savic-Jovcic et al.
grid spacing of 10 km and 80 hybrid vertical levels. The RAQDPS is run twice per
day to provide 48 h forecasts of Canada’s national Air Quality Health Index (AQHI).
The AQHI has a range from 0 to 10+ and is a year-round, additive, no-threshold,
hourly, health-based AQ index. It was developed from daily time-series analysis of air
pollutant concentrations and mortality data and is based on a weighted sum of NO 2 ,
O 3 , and PM 2.5 concentrations [7]. RAQDPS forecasts provide point-specific values
of NO 2 , O 3 , and PM 2.5 concentrations to UMOS-AQ, a statistical post-processing
package for bias correction that can both compensate for systematic model errors
and account for unresolved subgrid-scale phenomena at selected points, namely AQ
station locations. RAQDPS forecasts are also used as first-guess fields for operational
objective analyses of hourly North American surface concentration fields for O 3 ,
NO 2 , PM 2.5 , PM 10 , and SO 2 [5].
45.2 Recent Updates to the RAQDPS
A new high-performance computing (HPC) system to support ECCC forecasting
was installed in 2017. The heart of the new HPC system consists of a pair of Cray
XC40 computers, each with 30,780 cores, which replaced two IBM Power7-based
massively parallel supercomputers. Before this major computing system transition
a decision was made that no new forecast model versions should be introduced into
operations during the transition. The version of the RAQDPS that was operational
at the beginning of 2017, version 018, went into service in autumn 2016 [2]. It thus
continued to run on the IBM supercomputers until autumn 2017, when it was replaced
by equivalent code (version 019) that had been ported to the Cray supercomputers.
During 2017, work also continued in parallel to develop a new version of the
RAQDPS for implementation after the HPC transition. This new version, version 020,
has many changes and upgrades, including the following five major improvements:
(1) The RAQDPS follows the same meteorological initialization procedure as the
regional configuration of the GEM meteorological forecast model, the Regional
Deterministic Prediction System (RDPS; [1]). RDPS5, the pre-transition operational RDPS version, employs an intermittent data assimilation cycle and a digital filter, but RDPS6, the new RDPS version, employs a continuous data assimilation cycle and an incremental analysis update (IAU) approach. RAQDPS020
has also adopted this new initialization procedure.
(2) Meteorological lateral boundary conditions (LBCs), sometimes referred to as
“piloting files”, are provided to the limited-area RAQDPS every hour by the
RDPS. RAQDPS020 has adopted the RDPS6 as its piloting model in place of
RDPS5.
(3) The GEM-MACH code used in the RAQDPS has been updated from v2.2.0 to
v2.3.1 for RAQDPS020. Several features have been added: (a) modifications
to the gas-phase dry deposition module for snow-covered surfaces and sea ice;
(b) a new capability to turn off chemistry calculations at upper levels; and (c)
V. Savic-Jovcic et al.
grid spacing of 10 km and 80 hybrid vertical levels. The RAQDPS is run twice per
day to provide 48 h forecasts of Canada’s national Air Quality Health Index (AQHI).
The AQHI has a range from 0 to 10+ and is a year-round, additive, no-threshold,
hourly, health-based AQ index. It was developed from daily time-series analysis of air
pollutant concentrations and mortality data and is based on a weighted sum of NO 2 ,
O 3 , and PM 2.5 concentrations [7]. RAQDPS forecasts provide point-specific values
of NO 2 , O 3 , and PM 2.5 concentrations to UMOS-AQ, a statistical post-processing
package for bias correction that can both compensate for systematic model errors
and account for unresolved subgrid-scale phenomena at selected points, namely AQ
station locations. RAQDPS forecasts are also used as first-guess fields for operational
objective analyses of hourly North American surface concentration fields for O 3 ,
NO 2 , PM 2.5 , PM 10 , and SO 2 [5].
45.2 Recent Updates to the RAQDPS
A new high-performance computing (HPC) system to support ECCC forecasting
was installed in 2017. The heart of the new HPC system consists of a pair of Cray
XC40 computers, each with 30,780 cores, which replaced two IBM Power7-based
massively parallel supercomputers. Before this major computing system transition
a decision was made that no new forecast model versions should be introduced into
operations during the transition. The version of the RAQDPS that was operational
at the beginning of 2017, version 018, went into service in autumn 2016 [2]. It thus
continued to run on the IBM supercomputers until autumn 2017, when it was replaced
by equivalent code (version 019) that had been ported to the Cray supercomputers.
During 2017, work also continued in parallel to develop a new version of the
RAQDPS for implementation after the HPC transition. This new version, version 020,
has many changes and upgrades, including the following five major improvements:
(1) The RAQDPS follows the same meteorological initialization procedure as the
regional configuration of the GEM meteorological forecast model, the Regional
Deterministic Prediction System (RDPS; [1]). RDPS5, the pre-transition operational RDPS version, employs an intermittent data assimilation cycle and a digital filter, but RDPS6, the new RDPS version, employs a continuous data assimilation cycle and an incremental analysis update (IAU) approach. RAQDPS020
has also adopted this new initialization procedure.
(2) Meteorological lateral boundary conditions (LBCs), sometimes referred to as
“piloting files”, are provided to the limited-area RAQDPS every hour by the
RDPS. RAQDPS020 has adopted the RDPS6 as its piloting model in place of
RDPS5.
(3) The GEM-MACH code used in the RAQDPS has been updated from v2.2.0 to
v2.3.1 for RAQDPS020. Several features have been added: (a) modifications
to the gas-phase dry deposition module for snow-covered surfaces and sea ice;
(b) a new capability to turn off chemistry calculations at upper levels; and (c)