The phrase "autumn gradually" is correct and usable in written English.
It can be used to describe the slow transition or changes that occur during the autumn season.
Example: "As autumn gradually approached, the leaves began to change color and the air turned crisp."
Alternatives: "fall slowly" or "autumn slowly".
The hardening treatments were implemented in growth chambers under conditions simulating natural autumn conditions: gradually increasing night length combined with decreasing and diurnally fluctuating air temperature.
Separately, a cross-party group of backbenchers led by Grant Shapps, and including the Labour MPs Lucy Powell and Ian Austin, called for air passenger duty to be cut by 50% in the autumn statement – and gradually reduced over time – to boost Britain's trade performance in the wake of the Brexit vote.
Analysis on seasonal epidemic in key provinces showed that in recent years the spring incidence peak of different types of epidemic areas presented a downward trend while autumn-winter peak gradually increased, also suggesting that the proportion of Apodemus-type infection in China had been increasing.
Mary recovered during the autumn and winter, and gradually won over George Douglas to her own cause.
But in August, the Fed said its purchase of $300 billion in Treasury securities would slow gradually through the autumn before concluding at the end of October.
The Showa crater, which is located approximately 500 m east of the Minami-dake crater, resumed eruptive activity in June 2006, and vulcanian eruptions gradually increased in the autumn of 2009, as shown in Fig. 2.
Accordingly, the prevalence of 25(OH D levels at < 75 nmol/L and < 50 nmol/L decreased gradually from winter to autumn among those older children.
The survivors gradually returned to Brest during the autumn, the last arriving in early 1807.
With the arrival of autumn the forests and woodlands of the Northern Hemisphere are gradually transforming into a striking natural show of russet, vermillion, gold, bronze and yellow.
In this research, the ratio decreased gradually and ranged from 0.10 to 0.37 in autumn tea.
