On the occurrence and transport of biomass burning haze in south-southeast Asia using observation data and computational methods

Biomass-burning haze (BBH) is an environmental concern which has a tremendous impact on human health and the economy in Southeast Asia (SEA). One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude is uncharacteristic of the seasonality of extreme fire events which usually occur between August and October in the Maritime Continent (MC). Previous studies on the June 2013 event mostly include statistical studies of the impacts of haze on air quality and health. Therefore, this study aims to investigate the phenomenology of this peculiar haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness (AOT) retrievals, satellite based precipitation retrievals and meteorological indices. Particular attention is given to El Niño Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO) conditions since these phenomena influence inter-annual and intra-seasonal fire-activity, respectively, as well as the influence of tropical cyclones (TC) over the South China Sea. The above datasets are then supported by a WRF-Chem nested simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. Indeed, while the use of weather models to study BBH has become more popular, more modelling efforts need to be put into studying the June 2013 haze event to identify the mechanisms of long range transport of haze. A set of 13 sensitivity simulations are run to determine the physics settings which best represent the meteorology over the model domain during the June 2013 haze episode. The physics options used in the sensitivity simulations are selected based on previous WRF physics sensitivity studies and work which include WRF simulations with domains over Asia and SEA. In particular, the microphysics, cumulus parameterisation and planetary boundary layer (PBL) schemes are looked into to obtain the best agreement to observation data. The output from the sensitivity simulations are evaluated with satellite based precipitation retrievals and ground station data over Malaysia. The simulations run with the Lin microphysics scheme, Betts-Miller-Janjić (BMJ) cumulus parameterisation scheme and Mellor-Yamada-Janjić (MYJ) planetary boundary layer scheme performed best overall. These best settings, based on the sensitivity studies, are then used in the numerical simulations which are evaluated with satellite and ground station data. The evaluation shows that model produces similar patterns and magnitudes of AOT and successfully captures the variations in smoke plume height when compared to MODIS AOD and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) aerosol extinction profile datasets. The analysis of the time series ENSO conditions and MODIS fire count show that while extreme fire events are more characteristic of El Niño years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June for the years 2003–2015. In addition, the highest ratio of 0.89 of fire count for SPM to MC for any month for the period 2001–2015 was recorded in June 2013. An early and active TC season, which could have been the result of a strong transiting MJO, occurred in June 2013. The results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of the strong MJO event contributed to the event. The simulations further show that downward vertical motion of at least 6 cm s-1 prevailed over Sumatra on 22 June when TC Bebinca was most intense, while upward vertical motion reaching at least 9 cm s-1 prevailed over the same region before TC Bebinca on 17 June. Indeed, smoke sources were concentrated under this particular region of subsidence, where surface PM2.5 concentrations reached at least 1000 µg m-3 on 22 June. Vertical cross-sections across the model domain also show that subsidence during phase 6 of the MJO prevailed over Sumatra. Intense and early TC seasons over the Western North Pacific can therefore be an indication of the occurrence of early and extreme haze events over the MC. The numerical simulations are also used to study the convective mechanisms which are responsible for uplifting biomass-burning haze in the troposphere. These mechanisms over Sumatra and Peninsular Malaysia are under-studied and their physical mechanisms remain unclear. The PM2.5 mass concentration, vertical wind speed plots at different levels and vertical cross-sections of major smoke plumes are analysed and the corresponding convective mechanisms identified. Three main convective mechanisms are identified, namely, orographic motion over the Barisan Mountains of Indonesia, morning convergence over the strait of Malacca and orographic motion over Peninsular Malaysia. Results show that smoke is lifted to heights of at least 10 km in the atmosphere due to orographic lifting over Peninsular Malaysia while the average plume height increased to higher than 2 km as TC Bebinca subsided, due to the resulting decrease in subsidence. The identified mechanisms are able to uplift the biomass-burning emissions to the upper troposphere and this could have significant long-range transport and global climatic effects

The uncharacteristic occurrence of the June 2013 biomass-burning haze event in Southeast Asia: effects of the Madden-Julian oscillation and tropical cyclone activity.

One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude was uncharacteristic of the seasonality of extreme fire events, which usually occur between August and October in the Maritime Continent (MC). This study aims to investigate the phenomenology of the June 2013 haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness retrievals, satellite-based precipitation retrievals, and meteorological indices. These datasets are then supported by a WRF-Chem simulation to provide a comprehensive picture of the event's meteorology and aerosol transport phenomenology. While extreme fire events are more characteristic of El Nino years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral El Nino/Southern Oscillation (ENSO) conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June 2003–2015. An early active tropical cyclone (TC) season occurred in 2013, and results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of a strong Madden–Julian Oscillation (MJO) event contributed to the event intensification. Results also show that Bebinca induced a decrease in surface relative humidity of at least 10% over Riau, where fire hotspots were concentrated

On the occurrence and transport of biomass burning haze in south-southeast Asia using observation data and computational methods

Biomass-burning haze (BBH) is an environmental concern which has a tremendous impact on human health and the economy in Southeast Asia (SEA). One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude is uncharacteristic of the seasonality of extreme fire events which usually occur between August and October in the Maritime Continent (MC). Previous studies on the June 2013 event mostly include statistical studies of the impacts of haze on air quality and health. Therefore, this study aims to investigate the phenomenology of this peculiar haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness (AOT) retrievals, satellite based precipitation retrievals and meteorological indices. Particular attention is given to El Niño Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO) conditions since these phenomena influence inter-annual and intra-seasonal fire-activity, respectively, as well as the influence of tropical cyclones (TC) over the South China Sea. The above datasets are then supported by a WRF-Chem nested simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. Indeed, while the use of weather models to study BBH has become more popular, more modelling efforts need to be put into studying the June 2013 haze event to identify the mechanisms of long range transport of haze. A set of 13 sensitivity simulations are run to determine the physics settings which best represent the meteorology over the model domain during the June 2013 haze episode. The physics options used in the sensitivity simulations are selected based on previous WRF physics sensitivity studies and work which include WRF simulations with domains over Asia and SEA. In particular, the microphysics, cumulus parameterisation and planetary boundary layer (PBL) schemes are looked into to obtain the best agreement to observation data. The output from the sensitivity simulations are evaluated with satellite based precipitation retrievals and ground station data over Malaysia. The simulations run with the Lin microphysics scheme, Betts-Miller-Janjić (BMJ) cumulus parameterisation scheme and Mellor-Yamada-Janjić (MYJ) planetary boundary layer scheme performed best overall. These best settings, based on the sensitivity studies, are then used in the numerical simulations which are evaluated with satellite and ground station data. The evaluation shows that model produces similar patterns and magnitudes of AOT and successfully captures the variations in smoke plume height when compared to MODIS AOD and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) aerosol extinction profile datasets. The analysis of the time series ENSO conditions and MODIS fire count show that while extreme fire events are more characteristic of El Niño years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June for the years 2003–2015. In addition, the highest ratio of 0.89 of fire count for SPM to MC for any month for the period 2001–2015 was recorded in June 2013. An early and active TC season, which could have been the result of a strong transiting MJO, occurred in June 2013. The results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of the strong MJO event contributed to the event. The simulations further show that downward vertical motion of at least 6 cm s-1 prevailed over Sumatra on 22 June when TC Bebinca was most intense, while upward vertical motion reaching at least 9 cm s-1 prevailed over the same region before TC Bebinca on 17 June. Indeed, smoke sources were concentrated under this particular region of subsidence, where surface PM2.5 concentrations reached at least 1000 µg m-3 on 22 June. Vertical cross-sections across the model domain also show that subsidence during phase 6 of the MJO prevailed over Sumatra. Intense and early TC seasons over the Western North Pacific can therefore be an indication of the occurrence of early and extreme haze events over the MC. The numerical simulations are also used to study the convective mechanisms which are responsible for uplifting biomass-burning haze in the troposphere. These mechanisms over Sumatra and Peninsular Malaysia are under-studied and their physical mechanisms remain unclear. The PM2.5 mass concentration, vertical wind speed plots at different levels and vertical cross-sections of major smoke plumes are analysed and the corresponding convective mechanisms identified. Three main convective mechanisms are identified, namely, orographic motion over the Barisan Mountains of Indonesia, morning convergence over the strait of Malacca and orographic motion over Peninsular Malaysia. Results show that smoke is lifted to heights of at least 10 km in the atmosphere due to orographic lifting over Peninsular Malaysia while the average plume height increased to higher than 2 km as TC Bebinca subsided, due to the resulting decrease in subsidence. The identified mechanisms are able to uplift the biomass-burning emissions to the upper troposphere and this could have significant long-range transport and global climatic effects

Evaluation of Satellite-Derived Surface Soil Moisture Products over Agricultural Regions of Canada

Soil moisture is a critical indicator for climate change and agricultural drought, but its measurement is challenging due to large variability with land cover, soil type, time, space and depth. Satellite estimates of soil moisture are highly desirable and have become more widely available over the past decade. This study investigates and compares the performance of four surface soil moisture satellite datasets over Canada, namely, Soil Moisture and Ocean Salinity Level 3 (SMOS L3), versions 3.3 and 4.2 of European Space Agency Climate Change Initiative (ESA CCI) soil moisture product and a recent product called SMOS-INRA-CESBIO (SMOS-IC) that contains corrections designed to reduce several known sources of uncertainty in SMOS L3. These datasets were evaluated against in situ networks located in mostly agricultural regions of Canada for the period 2012 to 2014. Two statistical comparison methods were used, namely, metrics for mean soil moisture and median of metrics. The results suggest that, while both methods show similar comparisons for regional networks, over large networks, the median of metrics method is more representative of the overall correlation and variability and is therefore a more appropriate method for evaluating the performance of satellite products. Overall, the SMOS products have higher daily temporal correlations, but larger biases, against in situ soil moisture than the ESA CCI products, with SMOS-IC having higher correlations and smaller variability than SMOS L3. The SMOS products capture daily wetting and drying events better than the ESA CCI products, with the SMOS products capturing at least 75% of observed drying as compared to 55% for the ESA CCI products. Overall, for periods during which there are sufficient observations, both SMOS products are more suitable for agricultural applications over Canada than the ESA CCI products, even though SMOS-IC is able to capture soil moisture variability more accurately than SMOS L3

The development of climate services to inform decisions about winter maintenance at different timescales

Snow and ice control programs are critical for the efficiency and safety of transportation systems in all winter climates. Tools that help road authorities plan for, assess, and communicate the relationship between climate and winter road maintenance (WRM) activities are needed. There is increasing evidence that the development of such Climate Services (CS) tools is an iterative, evolving, and long-term process between the producers and users of this climate information, which increases the usability and application of climate science. This paper presents a case study describing the co-production of a climate translation service for a Canadian road authority. The purpose of this study is to: 1) refine an existing Winter Severity Index (WSI) to better understand how winter weather translates into inter-annual variations in WRM activities using publicly available data; 2) apply the index to historical weather observations to assess the magnitude and significance of historical winter weather trends, and 3) apply the index to modelled climate data to project the impacts of climate change on WRM operations in Ontario, Canada. Results indicate that the WSI for Ontario highways has strong fit with maintenance activity, when measured as equipment-hours. Analysis of WRM trends over more than three decades shows that winter severity has increased in some areas and decreased in others. The climate change analysis reveals that winters will experience a reduction in winter severity into the coming century

The Uncharacteristic Occurrence of the June 2013 Biomass-Burning Haze Event in Southeast Asia: Effects of the Madden-Julian Oscillation and Tropical Cyclone Activity

One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude was uncharacteristic of the seasonality of extreme fire events, which usually occur between August and October in the Maritime Continent (MC). This study aims to investigate the phenomenology of the June 2013 haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness retrievals, satellite-based precipitation retrievals, and meteorological indices. These datasets are then supported by a WRF-Chem simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. While extreme fire events are more characteristic of El Nino years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral El Nino/Southern Oscillation (ENSO) conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June 2003–2015. An early active tropical cyclone (TC) season occurred in 2013, and results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of a strong Madden–Julian Oscillation (MJO) event contributed to the event intensification. Results also show that Bebinca induced a decrease in surface relative humidity of at least 10% over Riau, where fire hotspots were concentrated