2017.11.27/28 23rd AIM Int’l WS[Annex] Expected climate change in Aomori Prefecture
Future climate in Aomori prefecture, located in the northern part ofJapan, will get warmer than the present climate by more than 3°C under
the SRES A1B scenario. Since the apple favors chilly climates (annualmean temperature of 6 to 14°C) , projected future temperatureapproaches this upper limit.

Yoshimitsu Masaki

Table 1 Future temperature change (annual mean) in Aomori
Prefecture with the SRES A1B scenario using the data set ofaGlobal Warming Projection Vol. 8 provided by JapanMeteorological Agency.

Hirosaki University
Email: ymasaki@hirosaki-u.ac.jp[1] Introduction
In Tohoku Region, located in the northern part of Japan, the apple isone of the most common fruit crops. Although changing climates canpotentially threat apple production in the near future, few quantitative
assessments have been made so far. We present climate impact
assessments on apple production -- (1) sunburn and (2) frost damage -under future climate.

[°C]

Reference
1980-2000

Observed
1981-2010

Near future2016-2036

Future2076-2096

10.0
10.2
10.0
9.4
10.6

10.210.4
10.2
9.5
10.7+1.2+1.2+1.4+1.3+1.1+3.3+3.2+3.5+3.3+3.1

Hirosaki
Aomori
HachinoheMutsu
FukauraAomori Prefecture(Latitude: 41°N)

Tsukuba City
(Latitude: 36°N)

Sunburn risk

[2] Sunburn
What is sunburn?
Sunburn is an irreversible damage
on apple fruit skin. When skintemperature goes up beyond 52°C or
46-49°C, the skin turns black or brown(Fig. 1). Such damaged apples cannot
be sold as fresh fruits. In 2012, earlymaturing variety Tsugaru was severely
damaged by sunburn, 23% of apples
were not shipped as fresh fruits.

(a)

(b)

(a) 1981-1999

Fig. 1 Apple farmers’ dilemma between
sunshine and sunburn. (a) Apples require
sunshine to make their skin red. However,(b) too much sunshine brings sunburndamage on the fruit skin.

More risks of sunburn in September in the end of this century(b) 2077-2095

How to assess sunburn risk?
We evaluated skin temperature by solving heat budget on an apple
fruit as the worst-case condition (sunlit surface) under given climate
conditions (air temperarture, humidity, solar radiation, wind, etc.). Sincewind speed on apple skin is expected to be smaller than wind speed on
open field, the wind speed was reduced to 25%. Based on future climate
projection under the SRES A1B scenario (Table 1), the daily maximum
skin temperature was simulated during apple’s ripening season (July toOctober).
ResultsFig. 2 shows the result of the daily maximum skin temperature.
Sunburn risk (red or black) will increase in the future, both in seasonal
extension and severity: In the current climate, the daily maximumtemperature going up ≧46℃ mostly occurs in August, whereas in thefuture climate, this condition can occur even in September. Consecutive
high temperature days are also observed in July-August under the futureclimate. Number of hours exceeding the sunburn threshold temperature
will also increase in the future (Table 2).

Consecutive high temperature days may severely damage apples.

Fig. 2 Simulated (a) current and (b) future daily maximum temperature on apple skin at Hirosaki
with the SRES A1B scenario. The lower panel indicates apple crop calendar for different cultivars.
Table 2 Number of hours exceeding the threshold temperatures of sunburn. “Change” shows
the change ratio with respect to the 1981-1999 values.
Years

1981-1999
2017-2035
change [%]2077-2095
change [%][3] Frost damage
Why we consider frost damage despite warming climates?
Please see a schematic example (Fig. 3). Since global warming
raises air temperature, straightforwardly, frost risk will be reduced in thefuture (Fig. 3(b)). On the same time, growing season of plants will beadvanced due to high temperature (Fig. 3(c)). Considering the compound
effects of these two aspects is necessary to assess future frost risk. Some
plants have less tolerance against cold temperature during bud bursts orflowering (e.g., blue horizontal lines shown in Fig. 3).
How to assess frost risk? – Preliminary analysis
Plant growth can be modeled by effective cumulative temperature(ECT, hereafter), a degree-day index after a plant begins to growth (e.g.,January or February). By evaluating the ECT at the last frost date, we
judged whether a plant will experience the last frost at earlier/later growthstages under future climate.
Prior to the analysis, we determined the daily minimum temperature
at the last frost day by using historical meteorological records for 19912010. We obtained +2.0℃ as the air minimum temperature at the last frost
date. In this preliminary analysis, we neglected varying tolerance levels oftemperature against coldness for different growth stages, but introduced
a uniform tolerance temperature (+2.0℃) throughout the growth stages.
Results
Fig. 4 shows the results for Tohoku region under warming climate(SRES A1B). Last frost date will be advanced by 10 to 15 days at mostsites (Fig. 4(b)). Until this advanced last frost date in the future, a plant will
gain more ECT in the southern Tohoku area and less ECT in the northernor mountainous area (Fig. 4(d)).
Acknowledgment: Regional climate projection was originally simulated by Japan Meteorological Agency (JMA) (see Reference [1]). These data wereprovided through the database website of Data Integration and Analysis System (DIAS,DIAS-P).

Skin temperature ≧46℃
JulyAug.
Sept.
Oct.
440
419-4.8
602+36.8

36425
367
42+0.8 +68.0
489
97+34.3 +288.0000

July-Oct.
829
828-0.1
1188+43.3

Skin temperature ≧52℃
July
Aug.
Sept.
Oct.
175
3176
7+0.6 +133.3
187
23+6.9 +666.7

000000July-Oct.
178
183+2.8210+18.0(a) under present climates

(a)

(b)

(c)

(d)

Frost damage(b) warming climatesFig. 4 (a) The last frost date (DOY; day of year) under thecurrent climate. (b) Change in the last frost date in the future.
(c) Effective cumulative temperature from the reference date(Jan. 15) until the last frost date under the current climate. (d)Change in the effective cumulative temperature under thefuture climate.
(c) advancementof growing season

Frost damage

Fig. 3 Schematic explanation of future frost risk. Blue horizontal
lines show the tolerance temperature of this hypothetical plant
against frost (coldness): If the temperature gets below this level,
plants may be suffered from frost damage. In this example, (a)under the current climate, frost damage occurs just before
flowering. (b) If the temperature rises, frost risk will diminish
because the temperature will go well above the tolerance level. (c)However, growing stage of the plant will be advanced due to hightemperature, plants may be suffered from frost damage.

[References] 1) JMA (2013), Global Warming Projection Vol.8, 131pp.