Steve LaDochy

The Disappearance of Dense Fog in Los Angeles: Another Urban Impact?

Incidences of dense fog have been gradually disappearing from large cities around the world. In Los Angeles, the climate records show that dense fog may become another extinct specie. In the last 50 years, dense fog has been reduced by about half at two, busy, coastal Los Angeles airports. Not one, but two factors, can be seen as possible causes. Both the downtown Los Angeles urban heat island and the citys air pollution clean-up show a significant relationship to decreasing fog. This study correlates monthly and annual dense fog data recorded at Los Angeles International and Long Beach International airports since the 1950s with downtown Los Angeles temperature and particulate air pollution data. The El Niño—Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) values also explain interannual dense fog variability, with PDO showing a stronger relationship. Coastal sea surface temperatures also closely follow dense fog frequencies. Recent coastal cooling, since 1998, associated with a shift to the cool phase of PDO, has been associated with a rise in dense fog incidences.

Heat Waves in Southern California: Are They Becoming More Frequent and Longer Lasting?

Los Angeles is experiencing more heat waves and also more extreme heat days. These numbers have increased by 3.09°F (1.72°C) per century and 22.8 per century occurrences, respectively. Both have more than tripled over the past 100 years as a consequence of the steady warming of Los Angeles. Our research explores the daily maximum and minimum temperatures from 1906 to 2006 recorded by the Department of Water and Power (DWP) downtown station and Pierce College, a suburban valley location. The average annual maximum temperature in Los Angeles has warmed by 5.0°F (2.8°C), while the average annual minimum temperature has warmed by 4.2°F (2.3°C). The greatest rate of change was during the summer months for both maximum and minimum temperature, with late fall and early winter having the least rates of change. There was also an increase in heat wave duration. Heat waves lasting longer than six days occurred regularly after the 1970s but were nonexistent from the start of 1906 until 1956, when the first six-day heat wave was recorded. While heat days have increased dramatically in the past century, cold days, where minimum temperature is below 45°F (7.2°C), show a slight decreasing trend.

THUNDERSTORM CLIMATOLOGY BASED ON LIGHTNING DETECTOR DATA, MANITOBA, CANADA

Comparisons are made between thunderstorm data collected from a lightning detector network and from conventional climatic stations for the province of Manitoba, Canada. The greater resolution in time and space of lightning detector (direction finder) data makes it a valuable source of thunderstorm information and lends itself to some important applications. Data were collected for the forest fire season of 1985 using a network of 7 lightning direction finders distributed throughout the province. Some 67,912 cloud-to-ground lightning strikes were recorded by time and location during 122 thunderstorm days. July was the most active month with 27,260 strikes over 28 days. Two regions of the province had the greatest concentration of lightning strikes, indicating some influence by topography and position of large lakes. Case studies are presented of the most active lightning storms of 1985 and 1986. These storms are exclusively frontal storms, with most having similar synoptic weather patterns to those of larg...

Improvements in Land-Use Classification for Estimating Daytime Surface Temperatures and Sea-Breeze Flows in Southern California

AbstractUnderstanding the interactions between large-scale atmospheric and oceanic circulation patterns and changes in land cover and land use (LCLU) due to urbanization is a relevant subject in many coastal climates. Recent studies by Lebassi et al. found that the average maximum air temperatures during the summer in two populated California coastal areas decreased at low-elevation areas open to marine air penetration during the period of 1970–2005. This coastal cooling was attributed to an increase in sea-breeze activity.The aims of this work are to better understand the coastal flow patterns and sea–land thermal gradient by improving the land-cover classification scheme in the region using updated airborne remote sensing data and to assess the suitability of the updated regional atmospheric modeling system for representing maritime flows in this region. This study uses high-resolution airborne data from the NASA Hyperspectral Infrared Imager (HyspIRI) mission preparatory flight campaign over Southern C...

Recent Online Resources and Distance Learning Experiences in Natural Hazards

The study of natural hazards is an effective way to capture the interest of students in the earth sciences. Recent natural disasters such as Hurricane Katrina and the December 2004 earthquake and tsunami in the Indian Ocean highlight the powerful magnitude of such events and our vulnerability to them. There are several effective ways to use online resources to study natural hazards. At CSULA, we have incorporated several online activities to enhance the learning experience in earth science classes. We have also piloted an online Natural Hazards course in addition to our traditionally-taught lecture course. We discuss the merits of the online course and the online activities used in our undergraduate earth science courses as well as review several other online resources useful for earth science education. Student surveys suggest that online activities increase student interest in the earth sciences. We share our experiences using online resources for the benefit of other instructors who are interested in adding multi-media to their earth science courses.