Since los angeles and phoenix are at the same latitude the intensity of insolation (amount of heat from the sun) at both locations is the if thats true, then explain the difference in the temperature curves for the two cities

As the Los Angeles is on the ocean, has a cooling effect from the winds.  Phoenix located in a valley and is at a higher elevation than LA.

Explanation:

It's Due to the temperature of the Los Angeles is close to the proximity with that of the ocean that moderates the temperature of the city and is the phoenix being away for the ocean get only abadiatic winds that keep this area warm and Los Angeles being closer to the ocean and thus the water takes more energy to cool and so when the warm air over the LA rises and the cool air goes to replace the climate. Thus the Los Angeles has temperatures of the 20°C in the day time and the temperature remains cool and calm whereas that of the phoenix remains hot and dry as the annual remains around mid '30s.

Answeris associated with sunny,dry weather;