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

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