Anticipating and responding to pavement performance as climate changes

As climate changes, the performance of pavements can be expected to change too. More rainfall can be expected to lead to softer subgrades and less sup-port to the pavement structure with consequences for more rapid cracking and rut-ting. Even if the amount of rainfall doesn’t change, many places can expect the rain to fall in less frequent but more intense storms leading to challenges for cur-rent pavement drainage systems. If temperature rises, then asphaltic pavements may be expected to suffer from greater rutting in hot weather; but if the tempera-ture rise causes greater evaporation then improved support conditions could arise; and if the temperature rise is in winter in an area that historically experiences fully frozen conditions in the winter, then weak, thawing pavements could result. Pre-dicting these and other effects of climate change involves an understanding of the sensitivity to climatic effects of both material properties and of overall pavement performance. In turn the predictions of such changes might indicate the need for adaptation in design, construction or materials selection – the extent of the need being dependent on the severity and risk associated with the predicted changes. In this way appropriate responses can be made to the challenges that future climate change will bring. In some places no change to practice may be required. Howev-er, for most authorities the immediate response should be to restate design codes and specifications with climate change in view. Mostly, the practices, techniques and tools for an adequate response are already available but users may need to employ adjusted practice if they don’t want future maintenance demands to be-come excessive

Aerosol specification in single-column Community Atmosphere Model version 5

Single-column model (SCM) capability is an important tool for general circulation model development. In this study, the SCM mode of version 5 of the Community Atmosphere Model (CAM5) is shown to handle aerosol initialization and advection improperly, resulting in aerosol, cloud-droplet, and ice crystal concentrations which are typically much lower than observed or simulated by CAM5 in global mode. This deficiency has a major impact on stratiform cloud simulations but has little impact on convective case studies because aerosol is currently not used by CAM5 convective schemes and convective cases are typically longer in duration (so initialization is less important). By imposing fixed aerosol or cloud-droplet and crystal number concentrations, the aerosol issues described above can be avoided. Sensitivity studies using these idealizations suggest that the Meyers et al. (1992) ice nucleation scheme prevents mixed-phase cloud from existing by producing too many ice crystals. Microphysics is shown to strongly deplete cloud water in stratiform cases, indicating problems with sequential splitting in CAM5 and the need for careful interpretation of output from sequentially split climate models. Droplet concentration in the general circulation model (GCM) version of CAM5 is also shown to be far too low (~ 25 cm^−3) at the southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site

Aerosol specification in single-column CAM5

Abstract. The ability to run a global climate model in single-column mode is very useful for testing model improvements because single-column models (SCMs) are inexpensive to run and easy to interpret. A major breakthrough in Version 5 of the Community Atmosphere Model (CAM5) is the inclusion of prognostic aerosol. Unfortunately, this improvement was not coordinated with the SCM version of CAM5 and as a result CAM5-SCM initializes aerosols to zero. In this study we explore the impact of running CAM5-SCM with aerosol initialized to zero (hereafter named Default) and test three potential fixes. The first fix is to use CAM5's prescribed aerosol capability, which specifies aerosols at monthly climatological values. The second method is to prescribe aerosols at observed values. The third approach is to fix droplet and ice crystal numbers at prescribed values. We test our fixes in four different cloud regimes to ensure representativeness: subtropical drizzling stratocumulus (based on the DYCOMS RF02 case study), mixed-phase Arctic stratocumulus (using the MPACE-B case study), tropical shallow convection (using the RICO case study), and summertime mid-latitude continental convection (using the ARM95 case study). Stratiform cloud cases (DYCOMS RF02 and MPACE-B) were found to have a strong dependence on aerosol concentration, while convective cases (RICO and ARM95) were relatively insensitive to aerosol specification. This is perhaps expected because convective schemes in CAM5 do not currently use aerosol information. Adequate liquid water content in the MPACE-B case was only maintained when ice crystal number concentration was specified because the Meyers et al. (1992) deposition/condensation ice nucleation scheme used by CAM5 greatly overpredicts ice nucleation rates, causing clouds to rapidly glaciate. Surprisingly, predicted droplet concentrations for the ARM95 region in both SCM and global runs were around 25 cm−3, which is much lower than observed. This finding suggests that CAM5 has problems capturing aerosol effects in this climate regime. </jats:p

On the Environmental Sustainability of Solar Technologies in a Coastal City

In this study, a first order environmental impact study of a large scale deployment of solar energy installed technologies in complex coastal urban environment is conducted. The work is motivated by the positive prospects of building integrated solar technologies as a sustainable alternative to energy demands and reduction of green house gases. Large scale deployment of solar technologies in rooftops of densely populated cities may have the potential of modifying surface energy budgets resulting in cooling or heating of the urban environment. To investigate this case the meso-scale model, Regional Atmospheric Modeling System (RAMS) is used, with a horizontal grid resolution of 4 km on an innermost grid over South Coast Air Basin (SocAB) region of Southern California. The simulation took place in summer 2002 where strong urban heat islands (UHIs) were observed for the region. The urban landscape was modified to represent a percentage of the rooftops with optical properties corresponding to solar PV and thermal collectors. Results show that the large scale presence of solar technologies in rooftops of SoCAB may have a net positive thermal storage effect enhancing the existing UHI by up to 0.3°F. This additional heat is advected inland as the sea-breeze develops warming further inland areas. The net environmental effect of solar technologies when compared with solar energy production was not investigated in this study.</jats:p

ES2007-36205 SPATIAL AND TEMPORAL CHANGES IN CLIMATOLOGICAL DEGREE-DAYS IN CALIFORNIA

ABSTRACT Analysis of 35 years observed trends in summertime daily maximum and minimum temperatures in two non attainment California air basins showed coastal cooling and inland warming. To study the impact of these results on the energy consumption we analyzed the cooling/heating degree days (CDD/HDD) of California long term observed temperatures. In this research historical surface 2-m air temperature data analyses consist of long-term data records, from 273 locations in California, and the primary sources of such data include the cooperative network, first order National Weather Service stations, and military weather stations. Data were used from 273 cooperative stations with more than 100 stations in the northern Central Valley (CV) of California, each with 40 to 60 years of monthly average, minimum, and maximum temperature data records. About 100 of the stations are in the San Francisco Bay (SFB) and 30 of the stations are on the South Coast Air Basin (SoCAB) of California. Analysis of the CDD/HDD has been undertaken for California in general and in the SFB and SoCAB in particular, under regional climate change conditions. Regional climate fluctuations have larger effects on surface temperatures, which in turn affect the CDD and HDD. A closer look to the CDD reflects an asymmetric increase between the coast and inland regions of California during the last 35 years. In general coastal areas experienced historical decrease of CDD while inland regions experienced increase in CDD. This is attributed to the sea breeze flows, which suggest an increase of the cold marine air intrusion due to the increase of the regional sea breeze potential, which naturally ventilates the coastal areas

Impacts of Climate Change in Degree Days and Energy Demand in Coastal California

An analysis of 1970–2005 observed summer daily maximum and minimum temperatures in two California air basins showed concurrent daytime coastal cooling and inland warming. To study the impacts of these results on energy consumption, summer cooling degree day (CDD) and winter heating degree day (HDD) trends were analyzed via these temperatures. The 2 m level air temperatures consisted of data from 159 locations in California, each with daily minimum and maximum values. Primary data sources included Cooperative Weather Station Network sites, first order National Weather Service stations, and military weather stations. An analysis of the CDD and HDD data has been undertaken for California, in general, and the San Francisco Bay Area and South Coast Air Basin, in particular, as the source of data for an analysis of energy-demand trends. Regional climate fluctuations have considerable effects on surface temperatures, which in turn affect CDD and HDD values. An asymmetric increase in summer CDD values between coastal and inland regions of California was found during the last 35 years, while winter HDD values showed decreases in most of California. In general, coastal areas experienced decreases of CDD, while inland regions experienced increases. The summer asymmetric increases in CDD is attributed to intensified sea breeze flows, which suggests increases in cold marine air intrusions over coastal land masses due to an increased regional sea breeze potential, which ventilates coastal areas, helps reduce maximum temperatures, and contributes to CDD decreases. An analysis of energy demands in the two air basins supports these climatological findings.</jats:p