Preliminary Results

1
California Surface Temperature Trends
W. Kessomkiat1, E. Cordero1, and L. Bereket2 1
Department of Meteorology, San José State
University, San José, CA, USA 2 Department of
Mechanical Engineering, Santa Clara University,
Santa Clara, CA, USA cordero_at_met.sjsu.edu
wittaya_at_met.sjsu.edu bereketl_at_yahoo.com
Preliminary Results California Max. and Min.
Temperature Trends from 1940-2005 Nor
thern and Southern California Max. and Min.
Temperature Trends from 1940-2005

• From Table 1., CAL, N-CAL, S-CAL Tmin trends
  during 1948-2005 are positive and statistically
  significant at the 95 confident level.
• For statistically significant trends
• N-CAL S-CAL CAL NH Global for Tmin.
• From Table 2., CAL, N-CAL, S-CAL Seasonal Tmin
  trends are positive and statistically significant
  at the 95 confident level except DJF in S-CAL.
  For CA climate regions, all regions annual Tmin
  are positive and statistically significant at the
  95 confident level except North Coast and
  South Interior region. In similarity, all
  seasonal Tmin are positive statistically
  significant at the 95 confident level except
  North Coast, North Central, South Interior
  regions.
• For statistically significant trends in different
  regions
• South Coast is the warmest 0.67 F/decade for
  Annual Tmin
• Mohave is the warmest 0.76 F/decade for DJF
  Tmin
• South Coast is the warmest 0.78 F/decade for
  MAM Tmin
• Mohave is the warmest 0.73 F/decade for JJA
  Tmin
• South Coast is the warmest 0.61 F/decade for
  SON Tmin
• Sacramento-Delta is the warmest 0.35 F/decade
  for DJF Tmax
• North Coast is the warmest 0.46 and 0.47
  F/decade for MAM and JJA Tmax respectively.

• Introduction
• Over decades, climate research has been conducted
  to determine whether the global temperature have
  increased as a result of the increase in
  anthropogenic greenhouse gases. The
  Intergovernmental Panel on Climate Change (IPCC)
  Fourth Assessment Report has recently shown the
  global temperature has been increasing since
  mid-twentieth century and that this was very
  likely (90 confidence) due to the increase in
  anthropogenic greenhouse gases. Our research is
  to study and understand how California
  temperature variations and the connection with
  anthropogenic forcing .
• Data and Methodologies
• The California temperature data is obtained from
  NCDC.
• (National Weather Service Cooperative
  Observers (Coop)
• stations)
• Data quality control and methods use the
  following criterias
• - no months are used if more than 6 days
  are
• missing.
• - seasons are defined using the
  standard
• meteorological definition.
• (winter DJF, spring MAM, summer
• JJA, and fall SON)
• - no seasons are used if more than one
  month
• is missing.
• - no annual value is used if more than
  one month
• is missing.
• All trends are computed via least squares
• regression.

Table. 1. Trends (ºF per decade) From Different
Time Periods for Maximum Annual Temperature,
Minimum Annual Temperature for Global land areas,
Northern Hemisphere, Northern and Southern
California, ( shows statistically significant
at 95 confident level)
Fig. 2 CAL Max. and Min. Annual Temperature
Table. 2. Annual and Seasonal Trends (ºF per
decade) From 1940-2005 for Maximum Temperature,
Minimum Temperature for Different Regions in
California ( shows statistically significant at
95 confident level)

• Summary
• Statistically significant warming trends (95
  confidence level) are observed over California in
  different climate regions.
• Annual Tmin Trends for CAL, N-CAL, S-CAL from
• 0.43 - 0.53 F/decade.
• Seasonal Tmin Trends for all climate regions
  from
• 0.17 - 0.78 F/decade
• California minimum temperatures are rising
  faster than maximum temperatures similar to
  global observations.
• Coastal regions are significantly warming faster
  than In-land regions as shown in North Coast JJA
  Tmax 0.47 F/decade and in South Coast MAM Tmin
  0.78 F/decade.
• Future Plans
• Perform additional data quality analysis
• Use output from climate models simulation to
  investigate role
• of anthropogenic forcing on CA temperature
  trends
• Acknowledgments. This work was supported in part
  NSFs Faculty Early Career Development (CAREER)
  Program, Grant ATM-0449996 and NASAs Living with
  a Star, Targeted Research and Technology Program,
  Grant LWS04-0025-0108

Fig. 3 N-CAL Max and Min Annual Temperature
Fig. 4 S-CAL Max and Min Annual Temperature
Fig. 1 Map of California Climate Weather Regions
(DRI) as shown in Table 2.